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  • 1.
    Foltynowicz, Aleksandra
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Schmidt, Florian M.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Gustafsson, Jörgen
    School of Engineering, Jönköping University, Jönköping, Sweden.
    Axner, Ove
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wavelength modulation absorption spectrometry from optically pumped collision broadened atoms and molecules2007In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 108, no 2, p. 220-238Article in journal (Refereed)
    Abstract [en]

    A theoretical investigation of the influence of optical pumping on wavelength modulation absorption spectrometry (WMAS) signals from collision broadened atoms and molecules is presented. General expressions for the nf-WMAS signal from atomic and molecular systems, modeled as three-level systems that can accommodate both optical saturation and optical pumping, are derived by the use of a previously developed Fourier series-based formalism in combination with rate equations solved under steady-state conditions. The expressions are similar to those describing the nf-WMAS signal from two-level systems that can accommodate optical saturation [Schmidt FM, Foltynowicz A, Gustafsson J, Axner O, WMAS from optically saturated collision-broadened transitions. JQSRT 2005;94:225–54], the difference being the value of the saturation flux, wherefore the general parametric dependence of WMAS signals from optically pumped systems is the same as that from optically saturated systems. The additional effect of optical pumping on the WMAS signal is investigated for three typical cases: molecules or atoms in an ordinary atmosphere, atoms in an inert atmosphere, and atoms or molecules possessing metastable states. The possibility to describe any of these systems with a two-level model is investigated.

  • 2.
    Germann, Matthias
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hjältén, Adrian
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Boudon, Vincent
    Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS/Université Bourgogne Franche-Comté, 9 Av. A. Savary, BP 47870, Dijon Cedex, France.
    Richard, Cyril
    Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS/Université Bourgogne Franche-Comté, 9 Av. A. Savary, BP 47870, Dijon Cedex, France.
    Krzempek, Karol
    Laser & Fiber Electronics Group, Faculty of Electronics, Photonics and Microsystems, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, Wrocław, Poland.
    Hudzikowski, Arkadiusz
    Laser & Fiber Electronics Group, Faculty of Electronics, Photonics and Microsystems, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, Wrocław, Poland.
    Głuszek, Aleksander
    Laser & Fiber Electronics Group, Faculty of Electronics, Photonics and Microsystems, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, Wrocław, Poland.
    Soboń, Grzegorz
    Laser & Fiber Electronics Group, Faculty of Electronics, Photonics and Microsystems, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, Wrocław, Poland.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    A methane line list with sub-MHz accuracy in the 1250 to 1380 cm−1 range from optical frequency comb Fourier transform spectroscopy2022In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 288, article id 108252Article in journal (Refereed)
    Abstract [en]

    We use a Fourier transform spectrometer based on a difference frequency generation optical frequency comb to measure high-resolution, low-pressure, room-temperature spectra of methane in the 1250 – 1380-cm−1 range. From these spectra, we retrieve line positions and intensities of 678 lines of two isotopologues: 157 lines from the 12CH4 ν4 fundamental band, 131 lines from the 13CH4 ν4 fundamental band, as well as 390 lines from two 12CH4 hot bands, ν2 + ν4 ν2 and 2ν4ν4. For another 165 lines from the 12CH4 ν4 fundamental band we retrieve line positions only. The uncertainties of the line positions range from 0.19 to 2.3 MHz, and their median value is reduced by a factor of 18 and 59 compared to the previously available data for the 12CH4 fundamental and hot bands, respectively, obtained from conventional FTIR absorption measurements. The new line positions are included in the global models of the spectrum of both methane isotopologues, and the fit residuals are reduced by a factor of 8 compared to previous absorption data, and 20 compared to emission data. The experimental line intensities have relative uncertainties in the range of 1.5 – 7.7%, similar to those in the previously available data; 235 new 12CH4 line intensities are included in the global model.

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  • 3.
    Germann, Matthias
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hjältén, Adrian
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Tennyson, Jonathan
    Department of Physics and Astronomy, University College London, Gower Street, London, United Kingdom.
    Yurchenko, Sergei N.
    Department of Physics and Astronomy, University College London, Gower Street, London, United Kingdom.
    Gordon, Iouli E.
    Center for Astrophysics, Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Pett, Christian
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Silander, Isak
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Krzempek, Karol
    Laser & Fiber Electronics Group, Faculty of Electronics, Photonics and Microsystems, Wrocław University of Science and Technology, Wrocław, Poland.
    Hudzikowski, Arkadiusz
    Laser & Fiber Electronics Group, Faculty of Electronics, Photonics and Microsystems, Wrocław University of Science and Technology, Wrocław, Poland.
    Głuszek, Aleksander
    Laser & Fiber Electronics Group, Faculty of Electronics, Photonics and Microsystems, Wrocław University of Science and Technology, Wrocław, Poland.
    Soboń, Grzegorz
    Laser & Fiber Electronics Group, Faculty of Electronics, Photonics and Microsystems, Wrocław University of Science and Technology, Wrocław, Poland.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Optical frequency comb Fourier transform spectroscopy of formaldehyde in the 1250 to 1390 cm−1 range: experimental line list and improved MARVEL analysis2024In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 312, article id 108782Article in journal (Refereed)
    Abstract [en]

    We use optical frequency comb Fourier transform spectroscopy to record high-resolution, low-pressure, room-temperature spectra of formaldehyde (H212C16O) in the range of 1250 to 1390 cm−1. Through line-by-line fitting, we retrieve line positions and intensities of 747 rovibrational transitions: 558 from the ν6 band, 129 from the ν4 band, and 14 from the ν3 band, as well as 46 from four different hot bands. We incorporate the accurate and precise line positions (0.4 MHz median uncertainty) into the MARVEL (measured active vibration-rotation energy levels) analysis of the H2CO spectrum. This increases the number of MARVEL-predicted energy levels by 82 and of rovibrational transitions by 5382, and substantially reduces uncertainties of MARVEL-derived H2CO energy levels over a large range: from pure rotational levels below 200 cm−1 up to multiply excited vibrational levels at 6000 cm−1. This work is an important step toward filling the gaps in formaldehyde data in the HITRAN database.

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  • 4.
    Gordon, I.E.
    et al.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Rothman, L.S.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Hargreaves, R.J.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Hashemi, R.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Karlovets, E.V.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Skinner, F.M.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Conway, E.K.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Hill, C.
    Nuclear Data Section, International Atomic Energy Agency, Vienna International Centre, PO Box 100, Vienna, Austria.
    Kochanov, R.V.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States; V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation; QUAMER laboratory, Tomsk State University, Tomsk, Russian Federation.
    Tan, Y.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States; Hefei National Laboratory for Physical Science at Microscale, University of Science and Technology of China, Hefei, China.
    Wcisło, P.
    Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University in Torun, Grudziadzka 5, Torun, Poland.
    Finenko, A.A.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States; Department of Chemistry, Lomonosov Moscow State University, Moscow, Russian Federation.
    Nelson, K.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Bernath, P.F.
    Department of Chemistry, Old Dominion University, VA, Norfolk, United States.
    Birk, M.
    German Aerospace Center (DLR), Remote Sensing Technology Institute, Wessling, Germany.
    Boudon, V.
    Laboratoire Interdisciplinaire Carnot de Bourgogne, Université de Bourgogne Franche-Comté, UMR 6303 CNRS, Dijon Cedex, France.
    Campargue, A.
    University of Grenoble Alpes, CNRS, LIPhy, Grenoble, France.
    Chance, K.V.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Coustenis, A.
    Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique, Paris Observatory, CNRS, PSL University, Sorbonne University, Paris, France.
    Drouin, B.J.
    Jet Propulsion Laboratory, California Institute of Technology, CA, Pasadena, United States.
    Flaud, J.M.
    Institut des Sciences Moléculaires d'Orsay, CNRS, Université Paris-Sud, Université Paris-Saclay, Orsay, France.
    Gamache, R.R.
    Department of Environmental, Earth & Atmospheric Sciences, University of Massachusetts, MA, Lowell, United States.
    Hodges, J.T.
    Chemical Sciences Division, National Institute of Standards and Technology, MD, Gaithersburg, United States.
    Jacquemart, D.
    Sorbonne Université, CNRS, De la MOlécule aux NAno-objets : Réactivité, Interactions et Spectroscopies, MONARIS, Paris, France.
    Mlawer, E.J.
    Atmospheric and Environmental Research, MA, Lexington, United States.
    Nikitin, A.V.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Perevalov, V.I.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Rotger, M.
    Groupe de Spectrométrie Moléculaire et Atmosphérique, UMR CNRS 7331, BP 1039, Reims Cedex 2, France.
    Tennyson, J.
    Department of Physics and Astronomy, University College London, London, United Kingdom.
    Toon, G.C.
    Jet Propulsion Laboratory, California Institute of Technology, CA, Pasadena, United States.
    Tran, H.
    Laboratoire de Météorologie Dynamique/IPSL, CNRS, Sorbonne Université, École normale supérieure, PSL Research University, École polytechnique, Paris, France.
    Tyuterev, V.G.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation; QUAMER laboratory, Tomsk State University, Tomsk, Russian Federation; Groupe de Spectrométrie Moléculaire et Atmosphérique, UMR CNRS 7331, BP 1039, Reims Cedex 2, France.
    Adkins, E.M.
    Chemical Sciences Division, National Institute of Standards and Technology, MD, Gaithersburg, United States.
    Baker, A.
    Division of Astronomy, California Institute of Technology, CA, Pasadena, United States.
    Barbe, A.
    Groupe de Spectrométrie Moléculaire et Atmosphérique, UMR CNRS 7331, BP 1039, Reims Cedex 2, France.
    Canè, E.
    Dipartimento di Chimica Industriale “Toso Montanari”, Università di Bologna, Viale Risorgimento 4, Bologna, Italy.
    Császár, A.G.
    MTA-ELTE Complex Chemical Systems Research Group, Budapest, Hungary; Eötvös Loránd University, Institute of Chemistry, Budapest, Hungary.
    Dudaryonok, A.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Egorov, O.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Fleisher, A.J.
    Chemical Sciences Division, National Institute of Standards and Technology, MD, Gaithersburg, United States.
    Fleurbaey, H.
    University of Grenoble Alpes, CNRS, LIPhy, Grenoble, France.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Furtenbacher, T.
    MTA-ELTE Complex Chemical Systems Research Group, Budapest, Hungary.
    Harrison, J.J.
    Department of Physics and Astronomy, University of Leicester, Leicester, United Kingdom; University of Leicester, National Centre for Earth Observation, Leicester, United Kingdom; University of Leicester, Leicester Institute for Space and Earth Observation, Leicester, United Kingdom.
    Hartmann, J.M.
    Laboratoire de Météorologie Dynamique/IPSL, CNRS, École polytechnique, Sorbonne Université, École normale supérieure, PSL Research University, Palaiseau, France.
    Horneman, V.M.
    Department of Physics, University of Oulu, Finland.
    Huang, X.
    SETI Institute, CA, Mountain View, United States.
    Karman, T.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Karns, J.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States; Golisano College of Computing and Information Sciences, Rochester Institute of Technology, NY, Rochester, United States; Computer Science Department, State University of New York at Oswego, NY, Oswego, United States.
    Kassi, S.
    University of Grenoble Alpes, CNRS, LIPhy, Grenoble, France.
    Kleiner, I.
    Université de Paris and Univ Paris Est Creteil, CNRS, LISA, Paris, France.
    Kofman, V.
    NASA Goddard Space Flight Center, MD, Greenbelt, United States.
    Kwabia-Tchana, F.
    Université de Paris and Univ Paris Est Creteil, CNRS, LISA, Paris, France.
    Lavrentieva, N.N.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Lee, T.J.
    Planetary Systems Branch, Space Science and Astrobiology Division, NASA Ames Research Center, CA, Moffett Field, United States.
    Long, D.A.
    Chemical Sciences Division, National Institute of Standards and Technology, MD, Gaithersburg, United States.
    Lukashevskaya, A.A.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Lyulin, O.M.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Makhnev, V.Yu.
    Institute of Applied Physics of Russian Academy of Sciences, Nizhny Novgorod, Russian Federation.
    Matt, W.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States; Computer Science Department, State University of New York at Oswego, NY, Oswego, United States.
    Massie, S.T.
    University of Colorado, Laboratory for Atmospheric and Space Physics, CO, Boulder, United States.
    Melosso, M.
    Dipartimento di Chimica “Giacomo Ciamician”, Università di Bologna, Via F. Selmi 2, Bologna, Italy.
    Mikhailenko, S.N.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Mondelain, D.
    University of Grenoble Alpes, CNRS, LIPhy, Grenoble, France.
    Müller, H.S.P.
    I. Physikalisches Institut, Universität zu Köln, Köln, Germany.
    Naumenko, O.V.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Perrin, A.
    Laboratoire de Météorologie Dynamique/IPSL, CNRS, Sorbonne Université, École normale supérieure, PSL Research University, École polytechnique, Paris, France.
    Polyansky, O.L.
    Department of Physics and Astronomy, University College London, London, United Kingdom; Institute of Applied Physics of Russian Academy of Sciences, Nizhny Novgorod, Russian Federation.
    Raddaoui, E.
    Sorbonne Université, CNRS, De la MOlécule aux NAno-objets : Réactivité, Interactions et Spectroscopies, MONARIS, Paris, France.
    Raston, P.L.
    Department of Chemistry and Biochemistry, James Madison University, VA, Harrisonburg, United States; Department of Chemistry, University of Adelaide, South Australia, Australia.
    Reed, Z.D.
    Chemical Sciences Division, National Institute of Standards and Technology, MD, Gaithersburg, United States.
    Rey, M.
    Groupe de Spectrométrie Moléculaire et Atmosphérique, UMR CNRS 7331, BP 1039, Reims Cedex 2, France.
    Richard, C.
    Laboratoire Interdisciplinaire Carnot de Bourgogne, Université de Bourgogne Franche-Comté, UMR 6303 CNRS, Dijon Cedex, France.
    Tóbiás, R.
    MTA-ELTE Complex Chemical Systems Research Group, Budapest, Hungary.
    Sadiek, I.
    Umeå University, Faculty of Science and Technology, Department of Physics. Leibniz Institute for Plasma Science and Technology (INP), Greifswald, Germany.
    Schwenke, D.W.
    Planetary Systems Branch, Space Science and Astrobiology Division, NASA Ames Research Center, CA, Moffett Field, United States.
    Starikova, E.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Sung, K.
    Jet Propulsion Laboratory, California Institute of Technology, CA, Pasadena, United States.
    Tamassia, F.
    Dipartimento di Chimica Industriale “Toso Montanari”, Università di Bologna, Viale Risorgimento 4, Bologna, Italy.
    Tashkun, S.A.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Vander Auwera, J.
    Université Libre de Bruxelles, Spectroscopy, Quantum Chemistry and Atmospheric Remote Sensing (SQUARES), C.P. 160/09, Brussels, Belgium.
    Vasilenko, I.A.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Vigasin, A.A.
    Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences, Pyzhevsky per. 3, Moscow, Russian Federation.
    Villanueva, G.L.
    NASA Goddard Space Flight Center, MD, Greenbelt, United States.
    Vispoel, B.
    Department of Environmental, Earth & Atmospheric Sciences, University of Massachusetts, MA, Lowell, United States; Research Unit Lasers and Spectroscopies (LLS), Institute of Life, Earth and Environment (ILEE), University of Namur (UNamur), Namur, Belgium; Royal Belgian Institute for Space Aeronomy (BIRA-IASB), Brussels, Belgium.
    Wagner, G.
    German Aerospace Center (DLR), Remote Sensing Technology Institute, Wessling, Germany.
    Yachmenev, A.
    Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, Hamburg, Germany; Hamburg Center for Ultrafast Imaging, Universität Hamburg, Luruper Chaussee 149, Hamburg, Germany.
    Yurchenko, S.N.
    Department of Physics and Astronomy, University College London, London, United Kingdom.
    The HITRAN2020 molecular spectroscopic database2022In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 277, article id 107949Article in journal (Refereed)
    Abstract [en]

    The HITRAN database is a compilation of molecular spectroscopic parameters. It was established in the early 1970s and is used by various computer codes to predict and simulate the transmission and emission of light in gaseous media (with an emphasis on terrestrial and planetary atmospheres). The HITRAN compilation is composed of five major components: the line-by-line spectroscopic parameters required for high-resolution radiative-transfer codes, experimental infrared absorption cross-sections (for molecules where it is not yet feasible for representation in a line-by-line form), collision-induced absorption data, aerosol indices of refraction, and general tables (including partition sums) that apply globally to the data. This paper describes the contents of the 2020 quadrennial edition of HITRAN. The HITRAN2020 edition takes advantage of recent experimental and theoretical data that were meticulously validated, in particular, against laboratory and atmospheric spectra. The new edition replaces the previous HITRAN edition of 2016 (including its updates during the intervening years). All five components of HITRAN have undergone major updates. In particular, the extent of the updates in the HITRAN2020 edition range from updating a few lines of specific molecules to complete replacements of the lists, and also the introduction of additional isotopologues and new (to HITRAN) molecules: SO, CH3F, GeH4, CS2, CH3I and NF3. Many new vibrational bands were added, extending the spectral coverage and completeness of the line lists. Also, the accuracy of the parameters for major atmospheric absorbers has been increased substantially, often featuring sub-percent uncertainties. Broadening parameters associated with the ambient pressure of water vapor were introduced to HITRAN for the first time and are now available for several molecules. The HITRAN2020 edition continues to take advantage of the relational structure and efficient interface available at www.hitran.org and the HITRAN Application Programming Interface (HAPI). The functionality of both tools has been extended for the new edition.

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  • 5.
    Hausmaninger, Thomas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Silander, Isak
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ma, Weiguang
    Umeå University, Faculty of Science and Technology, Department of Physics. Shanxi University, Taiyuan 030006, China.
    Axner, Ove
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Doppler-broadened NICE-OHMS beyond the cavity-limited weak absorption condition – II: experimental verification2016In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 168, p. 245-256Article in journal (Refereed)
    Abstract [en]

    Doppler-broadened (Db) noise-immune cavity-enhanced optical heterodyne molecular spectrometry (NICE-OHMS) is normally described by an expression, here termed the conventional (CONV) description, that is restricted to the conventional cavity-limited weak absorption condition (CCLWA), i.e. when the single pass absorbance is significantly smaller than the empty cavity losses, i.e. when α0L<<π/F. To describe NICE-OHMS signals beyond this limit two simplified extended descriptions (termed the extended locking and extended transmission description, ELET, and the extended locking and full transmission description, ELFT), which are assumed to be valid under the relaxed cavity-limited weak absorption condition (RCLWA), i.e. when α0L<π/Fα0L<π/F, and a full description (denoted FULL), presumed to be valid also when the α0L<π/Fα0L<π/F condition does not hold, have recently been derived in an accompanying work (Ma W, et al. Doppler-broadened NICE-OHMS beyond the cavity-limited weak absorption condition - I. Theoretical Description. J Quant Spectrosc Radiat Transfer, 2015, http://dx.doi.org/10.1016/j.jqsrt.2015.09.007, this issue). The present work constitutes an experimental verification and assessment of the validity of these, performed in the Doppler limit for a set of Fα0L/πFα0L/π values (up to 3.5); it is shown under which conditions the various descriptions are valid. It is concluded that for samples with Fα0L/πFα0L/π up to 0.01, all descriptions replicate the data well. It is shown that the CONV description is adequate and provides accurate assessments of the signal strength (and thereby the analyte concentration) up to Fα0L/πFα0L/π of around 0.1, while the ELET is accurate for Fα0L/πFα0L/π up to around 0.3. The ELFT description mimics the Db NICE-OHMS signal well for Fα0L/πFα0L/π up to around unity, while the FULL description is adequate for all Fα0L/πFα0L/π values investigated. Access to these descriptions both increases considerably the dynamic range of the technique and facilitates calibration using certified reference gases, which thereby significantly broadens the applicability of the Db NICE-OHMS technique.

  • 6.
    Hausmaninger, Thomas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Zhao, Gang
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ma, Weiguang
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Axner, Ove
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Depletion of the vibrational ground state of CH4 in absorption spectroscopy at 3.4 μm in N2 and air in the 1-100Torr range2018In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 205, p. 59-70Article in journal (Refereed)
    Abstract [en]

    A model presented in an accompanying work predicts that mid-IR absorption signals from methane in trace concentrations in various buffer gases detected at pressures in the 1-100Torr range can be reduced and distorted due to depletion of the vibrational ground state if the molecules are exposed to laser powers in the tens of mW range or above. This work provides experimental evidence of such depletion in a resonant cavity under a variety of conditions, e.g. for intracavity laser powers up to 2W and for buffer gases of N-2 or dry air, and verifies the applicability of the model. It was found that the degree of depletion is significantly larger in N-2 than dry air, and that it increases with pressure for pressures up to around 10Torr (attributed to a decreased diffusion rate) but decreases with pressure for pressures above 20Torr (caused by an increased collisional vibrational decay rate). The maximum degree of depletion (similar to 80%) was obtained for methane in N-2 at around 15Torr. This implies that absorption spectrometry of methane can experience significant non-linear dependencies on laser power, pressure, as well as buffer gas composition. It is shown that depletion takes place also in (CH4)-C-13, which verifies the applicability of the model also for this isotopologue, and that NICE-OHMS signals detected in absorption phase are less affected by depletion than in dispersion. It was concluded that the absorption mode of detection can provide concentration assessments that are virtually free of influence of depletion for intracavity powers below 0.8 W. 

  • 7.
    Hjältén, Adrian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sadiek, Ibrahim
    Umeå University, Faculty of Science and Technology, Department of Physics. Leibniz Institute for Plasma Science and Technology (INP), Greifswald, Germany.
    Line positions and intensities of the ν1 band of 12CH3I using mid-infrared optical frequency comb Fourier transform spectroscopy2023In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 306, article id 108646Article in journal (Refereed)
    Abstract [en]

    We present a new spectral analysis of the ν1 and ν3+ν1−ν3 bands of 12CH3I around 2971 cm−1 based on a high-resolution spectrum spanning from 2800 cm–1 to 3160 cm–1, measured using an optical frequency comb Fourier transform spectrometer. From this spectrum, we previously assigned the ν4 and ν3+ν4−ν3 bands around 3060 cm–1 using PGOPHER, and the line list was incorporated in the HITRAN database. Here, we treat the two fundamental bands, ν1 and ν4, together with the perturbing states, 2ν2+ν3 and ν2+2ν6±2, as a four-level system connected via Coriolis and Fermi interactions. A similar four-level system is assumed to connect the two ν3+ν1−ν3 and ν3+ν4−ν3 hot bands, which appear due to the population of the low-lying ν3 state at room temperature, with the 2ν2+2ν3 and ν2+ν3+2ν6±2 perturbing states. This spectroscopic treatment provides a good global agreement of the simulated spectra with experiment, and hence accurate line lists and band parameters of the four connected vibrational states in each system. It also allows revisiting the analysis of the ν4 and ν3+ν4−ν3 bands, which were previously treated as separate bands, not connected to their ν1 and ν3+ν1−ν3 counterparts. Overall, we assign 4665 transitions in the fundamental band system, with an average error of 0.00071 cm–1, a factor of two better than earlier work on the ν1 band using conventional Fourier transform infrared spectroscopy. The ν1 band shows hyperfine splitting, resolvable for transitions with J ≤ 2 × K. Finally, the spectral intensities of 65 lines of the ν1 band and 7 lines of the ν3+ν1−ν3 band are reported for the first time using the Voigt line shape as a model in multispectral fitting. The reported line lists and intensities will serve as a reference for high-resolution molecular spectroscopic databases, and as a basis for line selection in future monitoring applications of CH3I.

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  • 8.
    Hjältén, Adrian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Germann, Matthias
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Krzempek, Karol
    Laser & Fiber Electronics Group, Faculty of Electronics, Wrocław University of Science and Technology, Wroclaw, Poland.
    Hudzikowski, Arkadiusz
    Laser & Fiber Electronics Group, Faculty of Electronics, Wrocław University of Science and Technology, Wroclaw, Poland.
    Głuszek, Aleksander
    Laser & Fiber Electronics Group, Faculty of Electronics, Wrocław University of Science and Technology, Wroclaw, Poland.
    Tomaszewska, Dorota
    Laser & Fiber Electronics Group, Faculty of Electronics, Wrocław University of Science and Technology, Wroclaw, Poland.
    Soboń, Grzegorz
    Laser & Fiber Electronics Group, Faculty of Electronics, Wrocław University of Science and Technology, Wroclaw, Poland.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Optical frequency comb Fourier transform spectroscopy of 14N216O at 7.8 µm2021In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 271, article id 107734Article in journal (Refereed)
    Abstract [en]

    We use a Fourier transform spectrometer based on a compact mid-infrared difference frequency generation comb source to perform broadband high-resolution measurements of nitrous oxide, 14N216O, and retrieve line center frequencies of the ν1 fundamental band and the ν1 + ν2 – ν2 hot band. The spectrum spans 90 cm−1 around 1285 cm−1 with a sample point spacing of 3 × 10−4 cm−1 (9 MHz). We report line positions of 72 lines in the ν1 fundamental band between P(37) and R(38), and 112 lines in the ν1 + ν2 – ν2 hot band (split into two components with e/f rotationless parity) between P(34) and R(33), with uncertainties in the range of 90-600 kHz. We derive upper state constants of both bands from a fit of the effective ro-vibrational Hamiltonian to the line center positions. For the fundamental band, we observe excellent agreement in the retrieved line positions and upper state constants with those reported in a recent study by AlSaif et al. using a comb-referenced quantum cascade laser [J Quant Spectrosc Radiat Transf, 2018;211:172-178]. We determine the origin of the hot band with precision one order of magnitude better than previous work based on FTIR measurements by Toth [http://mark4sun.jpl.nasa.gov/n2o.html], which is the source of the HITRAN2016 data for these bands.

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  • 9.
    Ma, Weiguang
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan 030006, China.
    Silander, Isak
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hausmaninger, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Axner, Ove
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Doppler-broadened NICE-OHMS beyond the cavity-limited weak absorption condition – I. Theoretical Description2016In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 168, p. 217-244Article in journal (Other academic)
    Abstract [en]

    Doppler-broadened (Db) noise-immune cavity-enhanced optical heterodyne molecular spectrometry (NICE-OHMS) is conventionally described by an expression (here referred to as the CONV expression) that is restricted to the case when the single-pass absorbance, α0L, is much smaller than the empty cavity losses, π/F [here termed the conventional cavity-limited weak absorption (CCLWA) condition]. This limits the applicability of the technique, primarily its dynamic range and calibration capability. To remedy this, this work derives extended descriptions of Db NICEOHMS that are not restricted to the CCLWA condition. First, the general principles of Db NICEOHMS are scrutinized in some detail. Based solely upon a set of general assumptions, predominantly that it is appropriate to linearize the Beer–Lambert law, that the light is modulated to a triplet, and that the Pound–Drever–Hall sidebands are fully reflected, a general description of Db NICE-OHMS that is not limited to any specific restriction on α0L vs. π/F, here referred to as the FULL description, is derived. However, this description constitutes a set of equations to which no closed form solution has been found. Hence, it needs to be solved numerically (by iterations), which is inconvenient. To circumvent this, for the cases when α0Loπ/F but without the requirement that the stronger CCLWA condition needs to be fulfilled, a couple of simplified extended expressions that are expressible in closed analytical form, referred to as the extended locking and extended transmission description, ELET, and the extended locking and full transmission description, ELFT, have been derived. An analysis based on simulations validates the various descriptions and assesses to which extent they agree. It is shown that in the CCLWA limit, all extended descriptions revert to the CONV expression. The latter one deviates though from the extended ones for α0L around and above 0.1π/F. The two simplified extended descriptions agree with the FULL description for a larger range of α0L than the CONV expression, viz. for the ELET description for α0L up to 0.3π/F and for ELFT for α0L up to 0.6 or 1.0 π/F (depending on the mode of detection). It is then demonstrated that the conventional view of Db NICE-OHMS, which states that the out-of-phase and the in-phase signals can be referred to as a pure absorption and dispersion signal, respectively, breaks down when the CCLWA condition does not hold. In this case, the out-of-phase signal is additionally affected by the phase shifts of the laser components (i.e. dispersion) while the in-phase signal is also influenced by their attenuation. Access to new descriptions broadens considerably the dynamic range of Db NICE-OHMS and facilitates calibration using standard references samples, and thereby its applicability

  • 10.
    Rutkowski, Lucile
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Schmidt, Florian M.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Johansson, Alexandra C.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Khodabakhsh, Amir
    Kyuberis, Aleksandra A.
    Zobov, Nikolai F.
    Polyansky, Oleg L.
    Yurchenko, Sergei N.
    Tennyson, Jonathan
    An experimental water line list at 1950 K in the 6250–6670 cm−1 region2018In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 205, p. 213-219Article in journal (Refereed)
    Abstract [en]

    An absorption spectrum of (H2O)-O-16 at 1950 K is recorded in a premixed methane/air flat flame using a cavity-enhanced optical frequency comb-based Fourier transform spectrometer. 2417 absorption lines are identified in the 6250-6670 cm(-1) region with an accuracy of about 0.01 cm(-1). Absolute line intensities are retrieved using temperature and concentration values obtained by tunable diode laser absorption spectroscopy. Line assignments are made using a combination of empirically known energy levels and predictions from the new POKAZATEL variational line list. 2030 of the observed lines are assigned to 2937 transitions, once blends are taken into account. 126 new energy levels of (H2O)-O-16 are identified. The assigned transitions belong to 136 bands and span rotational states up to J = 27.

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  • 11.
    Rutkowski, Lucile
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Masłowski, Piotr
    Johansson, Alexandra C.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Khodabakhsh, Amir
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Optical frequency comb Fourier transform spectroscopy with sub-nominal resolution and precision beyond the Voigt profile2018In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 204, p. 63-73Article in journal (Refereed)
    Abstract [en]

    Broadband precision spectroscopy is indispensable for providing high fidelity molecular parameters for spectroscopic databases. We have recently shown that mechanical Fourier transform spectrometers based on optical frequency combs can measure broadband high-resolution molecular spectra undistorted by the instrumental line shape (ILS) and with a highly precise frequency scale provided by the comb. The accurate measurement of the power of the comb modes interacting with the molecular sample was achieved by acquiring single-burst interferograms with nominal resolution matched to the comb mode spacing. Here we describe in detail the experimental and numerical steps needed to achieve sub-nominal resolution and retrieve ILS-free molecular spectra, i.e. with ILS-induced distortion below the noise level. We investigate the accuracy of the transition line centers retrieved by fitting to the absorption lines measured using this method. We verify the performance by measuring an ILS-free cavity-enhanced low-pressure spectrum of the 3ν1 + ν3 band of CO2 around 1575 nm with line widths narrower than the nominal resolution. We observe and quantify collisional narrowing of absorption line shape, for the first time with a comb-based spectroscopic technique. Thus retrieval of line shape parameters with accuracy not limited by the Voigt profile is now possible for entire absorption bands acquired simultaneously.

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  • 12.
    Rutkowski, Lucile
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Masłowski, Piotr
    Johansson, Alexandra C.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Khodabakhsh, Amir
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Optical frequency comb Fourier transform spectroscopy with sub-nominal resolution and precision beyond the Voigt profile2018In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 204, p. 63-73Article in journal (Refereed)
    Abstract [en]

    Broadband precision spectroscopy is indispensable for providing high fidelity molecular parameters for spectroscopic databases. We have recently shown that mechanical Fourier transform spectrometers based on optical frequency combs can measure broadband high-resolution molecular spectra undistorted by the instrumental line shape (ILS) and with a highly precise frequency scale provided by the comb. The accurate measurement of the power of the comb modes interacting with the molecular sample was achieved by acquiring single-burst interferograms with nominal resolution matched to the comb mode spacing. Here we describe in detail the experimental and numerical steps needed to achieve sub-nominal resolution and retrieve ILS-free molecular spectra, i.e. with ILS-induced distortion below the noise level. We investigate the accuracy of the transition line centers retrieved by fitting to the absorption lines measured using this method. We verify the performance by measuring an ILS-free cavity-enhanced low-pressure spectrum of the 3ν1 + ν3 band of CO2 around 1575 nm with line widths narrower than the nominal resolution. We observe and quantify collisional narrowing of absorption line shape, for the first time with a comb-based spectroscopic technique. Thus retrieval of line shape parameters with accuracy not limited by the Voigt profile is now possible for entire absorption bands acquired simultaneously.

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  • 13.
    Rutkowski, Lucile
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Morville, Jerome
    Continuous Vernier filtering of an optical frequency comb for broadband cavity-enhanced molecular spectroscopy2017In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 187, p. 204-214Article in journal (Refereed)
    Abstract [en]

    We have recently introduced the Vernier-based Direct Frequency Comb Cavity-Enhanced Spectroscopy technique which allows us to record broadband spectra at high sensitivity and GHz resolution (Rutkowski and Morville, 2014) [1]. We discuss here the effect of Vernier filtering on the observed lineshapes in the 3v+delta band of water vapor and the entire A-band of oxygen around 800 nm in ambient air. We derive expressions for the absorption profiles resulting from the continuous Vernier filtering method, testing them on spectra covering more than 2000 cm(-1) around 12,500 cm(-1). With 31,300 independent spectral elements acquired at the second time scale, an absorption baseline noise of 2 x 10(-8) cm(-1) is obtained, providing a figure of merit of 1.1 x 10(-10) cm(-1)/root Hz per spectral element with a cavity finesse of 3000 and a cavity round-trip length around 3.3 m. 

  • 14.
    Sadiek, Ibrahim
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hjältén, Adrian
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Vieira, Francisco Senna
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Lu, Chuang
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stuhr, Michael
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Line positions and intensities of the ν4 band of methyl iodide using mid-infrared optical frequency comb Fourier transform spectroscopy2020In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 255, article id 107263Article in journal (Refereed)
    Abstract [en]

    We use optical frequency comb Fourier transform spectroscopy to measure high-resolution spectra of iodomethane, CH3I, in the C-H stretch region from 2800 to 3160 cm(-1). The fast-scanning Fourier transform spectrometer with auto-balanced detection is based on a difference frequency generation comb with repetition rate, f(rep), of 125 MHz. A series of spectra with sample point spacing equal to f rep are measured at different f rep settings and interleaved to yield sampling point spacing of 11 MHz. Iodomethane is introduced into a 76 m long multipass absorption cell by its vapor pressure at room temperature. The measured spectrum contains three main ro-vibrational features: the parallel vibrational overtone and combination bands centered around 2850 cm(-1), the symmetric stretch nu(1) band centered at 2971 cm(-1), and the asymmetric stretch nu(4) band centered at 3060 cm(-1). The spectra of the nu(4) band and the nearby nu(3)+nu(4)-nu(3) hot band are simulated using PGOPHER and a new assignment of these bands is presented. The resolved ro-vibrational structures are used in a least square fit together with the microwave data to provide the upper state parameters. We assign 2603 transitions to the nu(4) band with a standard deviation (observed - calculated) of 0.00034 cm(-1), and 831 transitions to the nu(3)+nu(4)-nu(3) hot band with a standard deviation of 0.00084 cm(-1). For comparison, in the earlier work using standard FT-IR with 162 MHz resolution [Anttila, et al., J. Mol. Spectrosc. 1986; 119:190-200] 1830 transition were assigned to the nu(4) band, and 380 transitions to the nu(3)+nu(4)-nu(3) hot band, with standard deviations of 0.00083 cm(-1) and 0.0013 cm(-1), respectively. The hyperfine splittings due to the 127 I nuclear quadrupole moment are observed for transitions with J <= 2 x K. Finally, intensities of 157 isolated transitions in the nu(4) band are reported for the first time using the Voigt line shape as a model in multispectral fitting.

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  • 15.
    Schmidt, Florian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Gustafsson, Jörgen
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Axner, Ove
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wavelength modulation absorption spectrometry from optically saturated collision-broadened transitions2005In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 94, no 2, p. 225-254Article in journal (Refereed)
    Abstract [en]

    A theoretical investigation of the influence of optical saturation on wavelength modulation absorption spectrometry (WMAS) signals from collision-broadened transitions is presented. Expressions are derived for the nth Fourier coefficient of the analytical detector signal, and thereby also for the nth harmonic signal from a WMAS instrumentation (i.e. the nf-WMAS signal), from a wavelength modulated collision-broadened transition exposed to optical saturation. The flux- (or irradiance-) and modulation-amplitude dependences of the nf-WMAS signal on resonance are scrutinized in detail. It is shown that the nth Fourier coefficient of the wavelength modulated analytical detector signal from an optically saturated collision-broadened transition can be written as a product of a flux-dependent (φ) bleaching function, given by (1+φ/φsat)-1 and identical to that appearing for ordinary, unmodulated absorption spectrometry (AS), and a flux-, detuning-, and modulation-amplitude-dependent wavelength modulated peak-normalized saturation-broadened Lorentzian lineshape function, specific for the WMAS technique. It is found that the nf-WMAS signal on resonance decreases faster than an ordinary AS signal as a function of laser flux when smaller-than-optimum modulation amplitudes are used, but slower when larger-than-optimum modulation amplitudes are used. When optimum (or close-to-optimum) modulation amplitudes are being used, on the other hand, the flux dependence of the WMAS signal resembles to a large degree that of ordinary AS. The conditions for when WMAS from collision-broadened transitions has the same flux dependence as ordinary AS are identified.

  • 16.
    Wang, Junyang
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ehlers, Patrick
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Silander, Isak
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Axner, Ove
    Umeå University, Faculty of Science and Technology, Department of Physics.
    On the accuracy of the assessment of molecular concentration and spectroscopic parameters by frequency modulation spectrometry and NICE-OHMS2014In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 136, p. 28-44Article in journal (Refereed)
    Abstract [en]

    Frequency modulation spectrometry (FMS), and thereby also noise immune cavity enhanced optical heterodyne molecular spectrometry (NICE-OHMS), can detect both absorption and dispersion signals, and can therefore, by curve fitting, extract molecular parameters from both these types of signals. However, parameters evaluated from the two modes of detection have been previously shown not to be identical. Their accuracy is affected by both the type of lineshape used by the fit and the accuracy of the detection phase. A thorough study is presented of the influence of three lineshape functions [Voigt, Rautian, and speed-dependent Voigt (SDV)] and errors in the detection phase on the retrieval of various molecular parameters, in particular the signal strength, which provides information about the concentration of molecules in a gas, from reference spectra in the 10-260 Torr region. It was found that for data detected and evaluated at pure absorption or dispersion phase by a system calibrated in the Doppler limit the signal strength can be underestimated at higher pressures by up to 45% if the evaluation is made using the Voigt profile. If the detection is plagued by phase errors additional inaccuracies, often in the order of percent per degree phase error (%/deg), can occur. More reliable parameters can be obtained if an appropriate lineshape function is used and the detection phase is considered a free parameter. However, despite this, none of the evaluation procedures can retrieve the molecular parameters fully correctly; the most accurate assessments of the signal strength, obtained when the data is detected close to absorption phase and evaluated by the SDV lineshape function, are still associated with an error of a few percent. (C) 2013 Elsevier Ltd. All rights reserved.

  • 17.
    Westberg, Jonas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Kluczynski, Pawel
    Lundqvist, Stefan
    Axner, Ove
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Analytical expression for the nth Fourier coefficient of a modulated Lorentzian dispersion lineshape function2011In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 112, no 9, p. 1443-1449Article in journal (Refereed)
    Abstract [en]

    Modulated spectroscopic detection techniques that rely on dispersion, e.g. Faraday modulation/rotation spectroscopy and wavelength-modulated noise-immune cavity-enhanced optical heterodyne molecular spectroscopy, are often described in terms of Fourier coefficients of a modulated dispersion lineshape function. This work derives a non-complex analytical expression for the nth Fourier coefficient of a modulated Lorentzian dispersion lineshape function. The expression is easier to implement, and orders of magnitude faster to execute, than previous approaches involving numerical calculations of integrals. The first six Fourier coefficients are explicitly given and illustrated for their optimum modulation amplitudes, which are also given

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  • 18.
    Westberg, Jonas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Lathdavong, Lemthong
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Dion, Claude M.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shao, Jie
    Institute of Information Optics of Zhejiang Normal University, Jinhua, China.
    Kluczynski, Pawel
    Siemens AB, Göteborg, Sweden.
    Lundqvist, Stefan
    Siemens AB, Göteborg, Sweden.
    Axner, Ove
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Quantitative description of Faraday modulation spectrometry in terms of the integrated linestrength and 1st Fourier coefficients of the modulated lineshape function2010In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 111, no 16, p. 2415-2433Article in journal (Refereed)
    Abstract [en]

    A quantitative description of the strength and shape of Faraday modulation spectrometry (FAMOS) signals is given. It is first shown how the signal can be expressed in terms of the integrated linestrength for the targeted transition, Si,j. Secondly, since the technique relies on a periodic modulation of the transition frequency induced by an alternating magnetic field, it is explicitly shown that it is possible to express the FAMOS signal concisely in terms of 1st Fourier coefficients of a magnetic-field-modulated dispersive lineshape function for left- and right-handed circularly polarized light. Expressions for the FAMOS signal in terms of the integrated linestrength and such Fourier coefficients are given for three cases: (i) for transitions between two arbitrary types of states, (ii) for transitions between two states that both belong to Hund’s coupling case (a), as is the case for rotational–vibrational transitions of NO, and finally (iii) for the commonly used Q-transitions between such states. It is finally shown that the FAMOS signal from a Q-transition can be expressed succinctly solely in terms of one 1st Fourier coefficient. A general analysis of FAMOS addressing an arbitrary Q-transition as well as the most sensitive Q3/2(3/2) transition in NO is given. The conditions for maximum signal are specifically identified.

  • 19.
    Westberg, Jonas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wang, Junyang
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Axner, Ove
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Fast and non-approximate methodology for calculation of wavelength-modulated Voigt lineshape functions suitable for real-time curve fitting2012In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 113, no 16, p. 2049-2057Article in journal (Refereed)
    Abstract [en]

    Wavelength modulation (WM) produces lock-in signals that are proportional to various Fourier coefficients of the modulated lineshape function of the molecular transition targeted. Unlike the case for the Lorentzian lineshape function, there is no known analytical expression for the Fourier coefficients of a modulated Voigt lineshape function; they consist of nested integrals that have to be solved numerically, which is often time-consuming and prevents real-time curve fitting. Previous attempts to overcome these limitations have so far consisted of approximations of the Voigt lineshape function, which brings in inaccuracies. In this paper we demonstrate a new means to calculate the lineshape of nf-WM absorption signals from a transition with a Voigt profile. It is shown that the signal can conveniently be expressed as a convolution of one or several Fourier coefficients of a modulated Lorentzian lineshape function, for which there are analytical expressions, and the Maxwell-Boltzmann velocity distribution for the system under study. Mathematically, the procedure involves no approximations, wherefore its accuracy is limited only by the numerical precision of the software used (in this case similar to 10(-16)) while the calculation time is reduced by roughly three orders of magnitude (10(-3)) as compared to the conventional methodology, i.e. typically from the second to the millisecond range. This makes feasible real-time curve fitting to lock-in output signals from modulated Voigt profiles. (C) 2012 Elsevier Ltd. All rights reserved.

  • 20.
    Westberg, Jonas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wang, Junyang
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Axner, Ove
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Methodology for fast curve fitting to modulated Voigt dispersion lineshape functions2014In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 133, p. 244-250Article in journal (Refereed)
    Abstract [en]

    Faraday rotation spectroscopy (FAMOS) as well as other modulated techniques that rely on dispersion produce lock-in signals that are proportional to various Fourier coefficients of modulated dispersion lineshape functions of the molecular transition targeted. In order to enable real-time curve fitting to such signals a fast methodology for calculating the Fourier coefficients of modulated lineshape functions is needed. Although there exist an analytical expression for such Fourier coefficients of modulated Lorentzian absorption and dispersion lineshape functions, there is no corresponding expression for a modulated Voigt dispersion function. The conventional computational route of such Fourier coefficients has therefore so far either consisted of using various approximations to the modulated Voigt lineshape function or solving time-consuming integrals, which has precluded accurate real-time curve fitting. Here we present a new methodology to calculate Fourier coefficients of modulated Voigt dispersion lineshape functions that is significantly faster (several orders of magnitude) and more accurate than previous approximative calculation procedures, which allows for real-time curve fitting to FAMOS signals also in the Voigt regime.

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