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Publications (10 of 25) Show all publications
Germann, M., Hjältén, A., Tennyson, J., Yurchenko, S. N., Gordon, I. E., Pett, C., . . . Foltynowicz, A. (2024). Optical frequency comb Fourier transform spectroscopy of formaldehyde in the 1250 to 1390 cm−1 range: experimental line list and improved MARVEL analysis. Journal of Quantitative Spectroscopy and Radiative Transfer, 312, Article ID 108782.
Open this publication in new window or tab >>Optical frequency comb Fourier transform spectroscopy of formaldehyde in the 1250 to 1390 cm−1 range: experimental line list and improved MARVEL analysis
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2024 (English)In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 312, article id 108782Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier, 2024
Keywords
Empirical line list, Formaldehyde, Fourier transform spectroscopy, Frequency comb spectroscopy, High-resolution spectroscopy, MARVEL
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:umu:diva-215854 (URN)10.1016/j.jqsrt.2023.108782 (DOI)2-s2.0-85174165539 (Scopus ID)
Funder
Knut and Alice Wallenberg Foundation, KAW 2015.0159Knut and Alice Wallenberg Foundation, KAW 2020.0303Swedish Research Council, 2016-03593Swedish Research Council, 2020-00238EU, Horizon 2020, 883830
Available from: 2023-11-02 Created: 2023-11-02 Last updated: 2023-11-10Bibliographically approved
Zakrisson, J., Silander, I., Silva de Oliveira, V., Hjältén, A., Rosina, A., Rubin, T., . . . Axner, O. (2024). Procedure for automated low uncertainty assessment of empty cavity mode frequencies in Fabry-Pérot cavity based refractometry. Optics Express, 32(3), 3959-3973
Open this publication in new window or tab >>Procedure for automated low uncertainty assessment of empty cavity mode frequencies in Fabry-Pérot cavity based refractometry
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2024 (English)In: Optics Express, E-ISSN 1094-4087, Vol. 32, no 3, p. 3959-3973Article in journal (Refereed) Published
Abstract [en]

A procedure for automated low uncertainty assessment of empty cavity mode frequencies in Fabry-Pérot cavity based refractometry that does not require access to laser frequency measuring instrumentation is presented. It requires a previously well-characterized system regarding mirror phase shifts, Gouy phase, and mode number, and is based on the fact that the assessed refractivity should not change when mode jumps take place. It is demonstrated that the procedure is capable of assessing mode frequencies with an uncertainty of 30 MHz, which, when assessing pressure of nitrogen, corresponds to an uncertainty of 0.3 mPa.

National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:umu:diva-220868 (URN)10.1364/OE.513708 (DOI)38297605 (PubMedID)2-s2.0-85183822866 (Scopus ID)
Funder
Swedish Research Council, 2020-00238Swedish Research Council, 2020-05105Knut and Alice Wallenberg Foundation, 2020.0303Umeå University, IDS-18Vinnova, 2018-04570
Available from: 2024-02-19 Created: 2024-02-19 Last updated: 2024-02-19Bibliographically approved
Hjältén, A., Silva de Oliveira, V., Silander, I., Rosina, A., Rutkowski, L., Sobon, G., . . . Foltynowicz, A. (2023). Accurate measurement and assignment of high rotational energy levels of the 3v3 ← v3 band of methane. In: 2023 conference on lasers and electro-optics, CLEO 2023: . Paper presented at 2023 Conference on Lasers and Electro-Optics, CLEO 2023, San Jose, May 7-12, 2023. IEEE, Article ID STh4L.4.
Open this publication in new window or tab >>Accurate measurement and assignment of high rotational energy levels of the 3v3 ← v3 band of methane
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2023 (English)In: 2023 conference on lasers and electro-optics, CLEO 2023, IEEE, 2023, article id STh4L.4Conference paper, Published paper (Refereed)
Abstract [en]

We use optical-optical double-resonance spectroscopy with a high-power continuous wave pump and a cavity-enhanced comb probe to expand sub-Doppler measurements of the 3v3 ← v3 band of CH4 to higher rotational levels. We assign the final states using combination differences, i.e., by reaching the same state using different pump/probe combinations.

Place, publisher, year, edition, pages
IEEE, 2023
Series
Quantum Electronics and Laser Science, ISSN 2160-8989
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:umu:diva-217340 (URN)2-s2.0-85176362960 (Scopus ID)9781957171258 (ISBN)9781665455688 (ISBN)
Conference
2023 Conference on Lasers and Electro-Optics, CLEO 2023, San Jose, May 7-12, 2023
Available from: 2023-12-04 Created: 2023-12-04 Last updated: 2023-12-04Bibliographically approved
Hjältén, A., Silva de Oliveira, V., Silander, I., Rosina, A., Rutkowski, L., Soboń, G., . . . Foltynowicz, A. (2023). Accurate measurement and assignment of high rotational energy levels of the 3ν3 ← ν3 band of methane. In: CLEO 2023: . Paper presented at 2023 Conference on Lasers and Electro-Optics (Science and Innovations), CLEO 2023, San Jose, May 7-12, 2023. Optical Society of America
Open this publication in new window or tab >>Accurate measurement and assignment of high rotational energy levels of the 3ν3 ← ν3 band of methane
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2023 (English)In: CLEO 2023, Optical Society of America, 2023Conference paper, Published paper (Refereed)
Abstract [en]

We use optical-optical double-resonance spectroscopy with a high-power continuous wave pump and a cavity-enhanced comb probe to expand sub-Doppler measurements of the 3ν3←ν3 band of CH4 to higher rotational levels. We assign the final states using combination differences, i.e., by reaching the same state using different pump/probe combinations.

Place, publisher, year, edition, pages
Optical Society of America, 2023
Series
Technical Digest Serie
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:umu:diva-224115 (URN)10.1364/CLEO_SI.2023.STh4L.4 (DOI)2-s2.0-85191524330 (Scopus ID)9781957171258 (ISBN)
Conference
2023 Conference on Lasers and Electro-Optics (Science and Innovations), CLEO 2023, San Jose, May 7-12, 2023
Available from: 2024-05-27 Created: 2024-05-27 Last updated: 2024-05-27Bibliographically approved
Germann, M., Hjältén, A., Boudon, V., Richard, C., Tennyson, J., Yurchenko, S., . . . Foltynowicz, A. (2023). High accuracy line lists of CH4 and H2CO in the 8 µm range from optical frequency comb fourier transform spectroscopy. In: 2023 conference on lasers and electro-optics Europe & European quantum electronics conference (CLEO/Europe-EQEC): . Paper presented at 2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023, Munich, June 26-30, 2023. IEEE, Article ID 10232703.
Open this publication in new window or tab >>High accuracy line lists of CH4 and H2CO in the 8 µm range from optical frequency comb fourier transform spectroscopy
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2023 (English)In: 2023 conference on lasers and electro-optics Europe & European quantum electronics conference (CLEO/Europe-EQEC), IEEE, 2023, article id 10232703Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
IEEE, 2023
Series
Conference on Lasers & Electro-Optics Europe & International Quantum Electronics Conference, ISSN 2639-5452, E-ISSN 2833-1052
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:umu:diva-216799 (URN)10.1109/CLEO/EUROPE-EQEC57999.2023.10232703 (DOI)2-s2.0-85175718241 (Scopus ID)9798350345995 (ISBN)9798350346008 (ISBN)
Conference
2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023, Munich, June 26-30, 2023
Funder
Knut and Alice Wallenberg Foundation, 2015.0159Knut and Alice Wallenberg Foundation, 2020.0303Swedish Research Council, 2016-03593EU, European Research Council, 883830
Available from: 2023-11-21 Created: 2023-11-21 Last updated: 2023-11-21Bibliographically approved
Sadiek, I., Hjältén, A. & Foltynowicz, A. (2023). Line positions and intensities of 12CH3I around 2971 cm-1 from frequency comb fourier transform spectroscopy. In: CLEO 2023: Proceedings. Paper presented at 2023 Conference on Lasers and Electro-Optics, CLEO 2023, San Jose, USA, May 7-12, 2023. Optical Society of America, Article ID JTh2A.100.
Open this publication in new window or tab >>Line positions and intensities of 12CH3I around 2971 cm-1 from frequency comb fourier transform spectroscopy
2023 (English)In: CLEO 2023: Proceedings, Optical Society of America, 2023, article id JTh2A.100Conference paper, Published paper (Refereed)
Abstract [en]

We use the high-resolution spectrum of 12CH3I measured using a comb-based Fourier transform spectrometer to extend line assignments to the 2971 cm-1 region and introduce line positions and intensities of the V1 and v3+v1-v3 bands.

Place, publisher, year, edition, pages
Optical Society of America, 2023
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:umu:diva-216869 (URN)10.1364/CLEO_AT.2023.JTh2A.100 (DOI)2-s2.0-85176309023 (Scopus ID)9781957171258 (ISBN)
Conference
2023 Conference on Lasers and Electro-Optics, CLEO 2023, San Jose, USA, May 7-12, 2023
Available from: 2023-12-12 Created: 2023-12-12 Last updated: 2023-12-12Bibliographically approved
Hjältén, A., Foltynowicz, A. & Sadiek, I. (2023). Line positions and intensities of the ν1 band of 12CH3I using mid-infrared optical frequency comb Fourier transform spectroscopy. Journal of Quantitative Spectroscopy and Radiative Transfer, 306, Article ID 108646.
Open this publication in new window or tab >>Line positions and intensities of the ν1 band of 12CH3I using mid-infrared optical frequency comb Fourier transform spectroscopy
2023 (English)In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 306, article id 108646Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier, 2023
National Category
Atom and Molecular Physics and Optics Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-209110 (URN)10.1016/j.jqsrt.2023.108646 (DOI)001007953500001 ()2-s2.0-85159161690 (Scopus ID)
Funder
Knut and Alice Wallenberg Foundation, 2015.0159Knut and Alice Wallenberg Foundation, 2020.0303Swedish Research Council, 2016-03593Swedish Research Council, 2020-00238
Available from: 2023-06-08 Created: 2023-06-08 Last updated: 2023-11-13Bibliographically approved
Sadiek, I., Hjältén, A., Roberts, F. C., Lehman, J. H. & Foltynowicz, A. (2023). Optical frequency comb-based measurements and the revisited assignment of high-resolution spectra of CH2Br2 in the 2960 to 3120 cm−1 region. Physical Chemistry, Chemical Physics - PCCP, 25, Article ID 8743.
Open this publication in new window or tab >>Optical frequency comb-based measurements and the revisited assignment of high-resolution spectra of CH2Br2 in the 2960 to 3120 cm−1 region
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2023 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 25, article id 8743Article in journal (Refereed) Published
Abstract [en]

Brominated organic compounds are toxic ocean-derived trace gases that affect the oxidation capacity of the atmosphere and contribute to its bromine burden. Quantitative spectroscopic detection of these gases is limited by the lack of accurate absorption cross-section data as well as rigorous spectroscopic models. This work presents measurements of high-resolution spectra of dibromomethane, CH2Br2, from 2960 cm−1 to 3120 cm−1 by two optical frequency comb-based methods, Fourier transform spectroscopy and a spatially dispersive method based on a virtually imaged phased array. The integrated absorption cross-sections measured using the two spectrometers are in excellent agreement with each other within 4%. A revisited rovibrational assignment of the measured spectra is introduced, in which the progressions of features are attributed to hot bands rather than different isotopologues as was previously done. Overall, twelve vibrational transitions, four for each of the three isotopologues CH281Br2, CH279Br81Br, and CH279Br2, are assigned. These four vibrational transitions are attributed to the fundamental ν6 band and the nearby nν4 + ν6 − nν4 hot bands (with n = 1–3) due to the population of the low-lying ν4 mode of the Br–C–Br bending vibration at room temperature. The new simulations show very good agreement in intensities with the experiment as predicted by the Boltzmann distribution factor. The spectra of the fundamental and the hot bands show progressions of strong QKa(J) rovibrational sub-clusters. The band heads of these sub-clusters are assigned and fitted to the measured spectra, providing accurate band origins and the rotational constants for the twelve states with an average error of 0.0084 cm−1. A detailed fit of the ν6 band of the CH279Br81Br isotopologue is commenced after assigning 1808 partially resolved rovibrational lines, with the band origin, rotational, and centrifugal constants as fit parameters, resulting in an average error of 0.0011 cm−1.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2023
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:umu:diva-206029 (URN)10.1039/d2cp05881b (DOI)000946509500001 ()2-s2.0-85150414323 (Scopus ID)
Funder
Knut and Alice Wallenberg Foundation, 2015.0159Knut and Alice Wallenberg Foundation, 2020.0303Swedish Research Council, 2016-03593Swedish Research Council, 2020-00238Swedish Research Council, 2018-05973Swedish National Infrastructure for Computing (SNIC)
Available from: 2023-03-28 Created: 2023-03-28 Last updated: 2023-11-10Bibliographically approved
Germann, M., Hjältén, A., Gordon, I. E., Tennyson, J., Yurchenko, S., Krzempek, K., . . . Foltynowicz, A. (2023). Precision frequency comb spectroscopy in the 8 µm range. In: CLEO 2023: Proceedings. Paper presented at 2023 Conference on Lasers and Electro-Optics, CLEO 2023, San Jose, USA, May 7-12, 2023. Optical Society of America, Article ID AW4E.1.
Open this publication in new window or tab >>Precision frequency comb spectroscopy in the 8 µm range
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2023 (English)In: CLEO 2023: Proceedings, Optical Society of America, 2023, article id AW4E.1Conference paper, Published paper (Refereed)
Abstract [en]

We use Fourier transform spectroscopy based on a compact difference frequency generation comb source emitting around 8 μm to record broadband high-resolution spectra of molecules relevant to astrophysics and environmental monitoring. From the spectra we obtain line lists with sub-MHz accuracy, an order of magnitude better than previously available, and use them to refine theoretical models of these molecules. Here we report results for formaldehyde, for which the 8 μm range is missing in HITRAN.

Place, publisher, year, edition, pages
Optical Society of America, 2023
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:umu:diva-216879 (URN)10.1364/CLEO_AT.2023.AW4E.1 (DOI)2-s2.0-85176375313 (Scopus ID)9781957171258 (ISBN)
Conference
2023 Conference on Lasers and Electro-Optics, CLEO 2023, San Jose, USA, May 7-12, 2023
Available from: 2023-12-12 Created: 2023-12-12 Last updated: 2024-05-13Bibliographically approved
Hjältén, A. (2023). Precision molecular spectroscopy in the near- and mid-infrared using frequency comb-based Fourier transform spectrometers. (Doctoral dissertation). Umeå: Umeå University
Open this publication in new window or tab >>Precision molecular spectroscopy in the near- and mid-infrared using frequency comb-based Fourier transform spectrometers
2023 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Molekylär precisionsspektroskopi i det när- och mellaninfraröda med frekvenskamsbaserade Fouriertransformspektrometrar
Abstract [en]

Absorption spectroscopy is a powerful scientific tool for non-invasive and remote sensing applications ranging from atmospheric monitoring to astrophysics. In spectroscopic detection schemes it is necessary to have spectral models for any molecular species to be detected or quantified. Such models are often based on spectroscopic measurements or at the very least require experimental validation. The experimental data need to be accurate in terms of absorption line positions and intensities, but should also cover as many absorption lines as possible, i.e. broadband measurements are highly desirable.

Fourier transform spectroscopy (FTS) based on optical frequency combs (OFCs) can supply laboratory data that meet these requirements. OFCs provide a broad optical bandwidth and high spectral brightness, and also revolutionized our ability to measure optical frequencies, which had a profound impact on the frequency accuracy of spectroscopic measurements. The combination of OFCs and FTS, using the recently developed sub-nominal resolution technique, allows for measuring broadband absorption spectra with very high resolution, and a frequency accuracy provided by the OFCs. The aim of the work in this thesis was to expand the application of sub-nominal OFC-FTS to provide the much needed high-accuracy data for validation and development of spectroscopic databases of molecules relevant for a wide range of sensing application.

We developed a spectrometer to target the strong molecular absorption bands in the mid-infrared using two OFC sources based on difference frequency generation (DFG) emitting in the 3 μm and 8 μm wavelength ranges. We measured the spectra of iodomethane, CH3I, and dibromomethane, CH2Br2, around 3 μm, fitted Hamiltonian models to several bands using the PGOPHER software, and reported molecular constants. For CH3I we improved on previous models, while for CH2Br2 we presented a new interpretation of the spectrum. We also reported the first assessments of line intensities of CH3I performed using multispectral fitting. At 8 μm, we implemented OFC-FTS based on a fiber-based compact DFG OFC source and measured low pressure spectra of nitrous oxide, N2O, methane, CH4, and formaldehyde, H2CO. After the frequency accuracy was confirmed by excellent agreement with an earlier accurate study of N2O, we compiled extensive line lists for CH4 and H2CO containing hundreds of transition frequencies with a precision improved by one order of magnitude compared to previously available data, and also reported line intensities for most transitions. For CH4 the new data were used to improve a global Hamiltonian model, while the H2CO data were incorporated into an algorithm based on spectroscopic networks to yield better precision in predicted energy levels and transition frequencies.

We also further developed a recent implementation of double resonance (DR) spectroscopy where optical pumping by a continuous-wave laser was used to populate selected vibrational energy levels of CH4 not populated at room temperature, and a near-infrared OFC probed sub-Doppler transitions from the pumped states. Such measurements are necessary to validate theoretical predictions of transitions between excited vibrational levels that are relevant for high-temperature environments such as the atmospheres of hot celestial objects. We reported an improved measurement setup using a new pump laser, new enhancement cavity with an updated OFC-cavity locking scheme, and measured transitions between more highly excited rotational levels than was previously reported. The higher rotational excitations lead to a larger number of DR transitions, which could be readily detected in the broadband high-resolution OFC-FTS spectra. We retrieved parameters of 88 lines of which we could assign 79 to theoretically predicted transitions. We found systematic frequency discrepancies with the predictions, that had not been observed earlier for lower rotational levels.

These implementations of sub-nominal OFC-FTS thus provided highly accurate line lists and improved spectral models of absorption bands of several molecules in the universally important mid-infrared region, as well as the first detection of 88 transitions between excited vibrational states of CH4 relevant for high-temperature environments. We demonstrated the high potential of these techniques for collecting large amounts of accurate spectroscopic data, that further the scope of applicability of molecular spectroscopy.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2023. p. 94
Keywords
optical frequency comb, molecular spectroscopy, Fourier transform spectrometer, high resolution, mid-infrared, line list, double-resonance spectroscopy, difference frequency generation
National Category
Atom and Molecular Physics and Optics
Research subject
Physics
Identifiers
urn:nbn:se:umu:diva-216403 (URN)978-91-8070-131-0 (ISBN)978-91-8070-130-3 (ISBN)
Public defence
2023-12-07, NAT.D.480, Naturvetarhuset, Umeå, 09:00 (English)
Opponent
Supervisors
Available from: 2023-11-16 Created: 2023-11-10 Last updated: 2023-11-13Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-6144-4957

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