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Persson, Per-Axel
##### Publications (10 of 19) Show all publications
Persson, P.-A., Jacobsson, P., Stafström, S. & Sundqvist, B. (2000). Enhanced thermal dissociation of optically excited C60 chains.. Europhysics letters, 49(5), 631-636
Open this publication in new window or tab >>Enhanced thermal dissociation of optically excited C60 chains.
2000 (English)In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 49, no 5, p. 631-636Article in journal (Refereed) Published
##### Abstract [en]

The thermal dissociation of C60 polymers has been studied using Raman scattering. The measured dissociation rate depends on the intensity of the 1064 nm NIR excitation, showing that i) the band gap is smaller than 1.17 eV and ii) a radiation-enhanced thermal breakdown path exists in addition to the "normal'' thermal breakdown mechanism. Quantum chemical calculations show that the energy barrier Ea for thermal breakdown is about 40% lower in the first (optically) excited state than in the ground state. This agrees well with the ratio between our radiation-enhanced value $E_{a} = (1.1 \pm 0.02)\,eV$ and values near 1.9 eV measured by purely thermal methods.

##### Place, publisher, year, edition, pages
EDP Sciences, 2000
##### Keywords
Fullerenes, C60, polymers, thermal dissociation, optical excitation, polymer dissocation, molecular chains, orthorhombic polymer, fullerene polymer, quantum chemical calculations
##### National Category
Condensed Matter Physics
Physics
##### Identifiers
urn:nbn:se:umu:diva-22607 (URN)10.1209/epl/i2000-00197-2 (DOI)
Available from: 2009-05-14 Created: 2009-05-14 Last updated: 2018-06-08
Sundqvist, B., Wågberg, T., Persson, P.-A., Jacobsson, P., Stafström, S., Moret, R. & Launois, P. (2000). Structure and stability of pressure polymerized C60. In: Molecular Materials: Molecular Crystals and Liquid Crystals Section C, vol. 13: Proceedings of the 4th International Workshop on Fullerenes and Atomic Clusters (IWFAC'99), St. Petersburg 1999 (pp. 117-122). Overseas Publishers Association N.V.
Open this publication in new window or tab >>Structure and stability of pressure polymerized C60
2000 (English)In: Molecular Materials: Molecular Crystals and Liquid Crystals Section C, vol. 13: Proceedings of the 4th International Workshop on Fullerenes and Atomic Clusters (IWFAC'99), St. Petersburg 1999, Overseas Publishers Association N.V. , 2000, p. 117-122Conference paper, Published paper (Refereed)
##### Abstract [en]

We discuss the bond energy of the orthorhombic C60 polymer and the structure of the two-dimensional C60 polymers. For the orthorhombic polymer, measurements of the dissociation energy by different methods give results that differ by a factor of two. We show that optical excitations lead to a temporary weakening of the intermolecular bonds and optical measurements thus show a low apparent bond energy. We have also polymerized a single crystal of C60 into two-dimensional phases. X-ray diffraction studies of this crystal have enabled us to determine the stacking sequences of both the tetragonal and the rhombohedral structures.

##### Place, publisher, year, edition, pages
Overseas Publishers Association N.V., 2000
##### Series
Molecular Materials, ISSN 1058-7276 ; 13
##### Keywords
Fullerenes, C60, high pressure synthesis, fullerene polymers, polymer chains, two-dimensional polymers, optical excitation, bond energy, bond strength, X-ray diffraction, single crystal, orthorhombic, tetragonal, rhombohedral
##### National Category
Condensed Matter Physics
Physics
##### Identifiers
urn:nbn:se:umu:diva-23058 (URN)
Available from: 2009-05-27 Created: 2009-05-27 Last updated: 2018-06-08
Nagel, P., Pasler, V., Lebedkin, S., Soldatov, A., Meingast, C., Sundqvist, B., . . . Inaba, A. (1999). C60 one- and two-dimensional polymers, dimers, and hard fullerite: Thermal expansion, anharmonicity, and kinetics of depolymerization. Physical Review B. Condensed Matter and Materials Physics, 60(24), 16920-16927
Open this publication in new window or tab >>C60 one- and two-dimensional polymers, dimers, and hard fullerite: Thermal expansion, anharmonicity, and kinetics of depolymerization
1999 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 60, no 24, p. 16920-16927Article in journal (Refereed) Published
##### Abstract [en]

We report on high-resolution thermal expansion measurements of high-temperature-pressure treated C60 [one-dimensional (1D) and (2D) polymers and “hard fullerite”], as well as of C60 dimers and single crystal monomer C60 between 10 and 500 K. Polymerization drastically reduces the thermal expansivity from the values of monomeric C60 due to the stronger and less anharmonic covalent bonds between molecules. The expansivity of the “hard” material approaches that of diamond. The large and irreversible volume change upon depolymerization between 400 and 500 K makes it possible to study the kinetics of depolymerization, which is described excellently by a simple activated process, with activation energies of 1.9±0.1 eV (1D and 2D polymers) and 1.75±0.05 eV (dimer). Although the activation energies are very similar for the different polymers, the depolymerization rates differ by up to four orders of magnitude at a given temperature, being fastest for the dimers. Preliminary kinetic data of C70 polymers are presented as well.

##### Place, publisher, year, edition, pages
American Physical Society, 1999
##### Keywords
Fullerenes, C60, C70, fullerene polymers, high pressure synthesis, thermal depolymerization, thermal expansion, activation energy, dimers, linear polymer chains, two-dimensional polymers, hard fullerite, orthorhombic polymer, tetragonal polymer, diamond
##### National Category
Condensed Matter Physics
Physics
##### Identifiers
urn:nbn:se:umu:diva-23161 (URN)10.1103/PhysRevB.60.16920 (DOI)
Available from: 2009-06-02 Created: 2009-06-02 Last updated: 2018-06-08
Wågberg, T., Persson, P.-A. & Sundqvist, B. (1999). Structural evolution of low-pressure polymerised C60 with polymerisation conditions. Journal of Physics and Chemistry of Solids, 60(12), 1989-1994
Open this publication in new window or tab >>Structural evolution of low-pressure polymerised C60 with polymerisation conditions
1999 (English)In: Journal of Physics and Chemistry of Solids, ISSN 0022-3697, E-ISSN 1879-2553, Vol. 60, no 12, p. 1989-1994Article in journal (Refereed) Published
##### Abstract [en]

We show in this paper that characteristic features in the Raman spectra, especially the frequency of the pentagonal pinch mode, can give information about the polymeric structure of pressure polymerised C60. High-pressure treatment at 1 GPa below 510 K for 3 h results in the formation of a low fraction of dimers only, while treatment at the same pressure and time above 540 K affords a fully polymerised material. In the latter case, different relative fractions of dimers and polymer chains are obtained depending on whether the final reaction conditions were reached by isobaric or isothermal path. We suggest that this difference results from different reaction dynamics in the two cases. The polymerisation rate depends on T and p and on the rotational and orientational states of the molecules. At 1 GPa no polymerisation is observed in sc C60, while in “hexagon” oriented sc C60 at 1.7 GPa dimers are already formed 175 K below the fcc–sc transition and a fully polymerised material is obtained just below the transition to the fcc phase.

##### Place, publisher, year, edition, pages
Elsevier B.V., 1999
##### Keywords
Fullerenes, C60, high pressure, polymerization, Raman spectroscopy, dimers, orthorhombic polymers, molecular chains, orientational state
##### National Category
Condensed Matter Physics
Physics
##### Identifiers
urn:nbn:se:umu:diva-23188 (URN)10.1016/S0022-3697(99)00214-0 (DOI)
Available from: 2009-06-03 Created: 2009-06-03 Last updated: 2018-06-08
Nagel, P., Meingast, C., Persson, P.-A. & Sundqvist, B. (1998). High-resolution thermal expansion of high-pressure polymerized and 'normal' C60 from 10-500 K: Kinetics of depolymerization. In: Molecular Nanostructures: Proceedings of the International Winterschool on Electronic Properties of Novel Materials, Kirchberg 1997 (pp. 365-368). Singapore: World Scientific
Open this publication in new window or tab >>High-resolution thermal expansion of high-pressure polymerized and 'normal' C60 from 10-500 K: Kinetics of depolymerization
1998 (English)In: Molecular Nanostructures: Proceedings of the International Winterschool on Electronic Properties of Novel Materials, Kirchberg 1997, Singapore: World Scientific , 1998, p. 365-368Conference paper, Published paper (Refereed)
##### Abstract [en]

High-resolution capacitance dilatometry was used to study the thermal expansion of both 'normal' and polymer phases of C60. The expansivity, alpha(T), of 'normal' C60 exhibits an unusual temperature dependence above the orientational disordering transition at 260 K; alpha(T) decreases by about 30% from 260 to 500 K and appears to reach a minimum near 500 K. Polymerized C60 has a much smaller expansivity than normal C60 due to the stronger covalent bonding between molecules. The polymerized state converts back to 'normal' C60 at temperatures between 450 and 500 K. We show that this is an activated process with a well-defined activation energy of 1.92 eV and a volume increase of about 2%.

##### Place, publisher, year, edition, pages
Singapore: World Scientific, 1998
##### Keywords
Fullerenes, C60, thermal expansion, dilatometry, polymers, fullerene polymer
##### National Category
Condensed Matter Physics
Physics
##### Identifiers
urn:nbn:se:umu:diva-23482 (URN)981-02-3261-6 (ISBN)
##### Note
Editors: Hans Kuzmany, Jörg Fink, Michael Mehring and Siegmar Roth.Available from: 2009-06-20 Created: 2009-06-20 Last updated: 2018-06-08
Launois, P., Moret, R., Persson, P.-A. & Sundqvist, B. (1998). Pressure polymerized C60 single crystals: First x-ray diffraction results. In: Molecular Nanostructures: Proceedings of the International Winterschool on Electronic Properties of Novel Materials, Kirchberg 1997 (pp. 348-352). Singapore: World Scientific
Open this publication in new window or tab >>Pressure polymerized C60 single crystals: First x-ray diffraction results
1998 (English)In: Molecular Nanostructures: Proceedings of the International Winterschool on Electronic Properties of Novel Materials, Kirchberg 1997, Singapore: World Scientific , 1998, p. 348-352Conference paper, Published paper (Refereed)
##### Abstract [en]

C60 single crystals compressed at approx. 1 GPa and heated at about 300 C are found to polymerize in one dimension without losing their crystalline order. The resulting structure is orthrhombic, with space group Pmnn and parameters a=9.14 Å, b=9.9 Å and c=14.66 Å. The X-ray single crystal results allow us to derive a polymerization mechanism, which may also, for instance, apply to one dimensional C60 polymers in the doped compounds. The new polymer phase is discussed with respect to the C60 pressure-temperature diagram. The comparison with the A1C60 polymers raises questions about the interchain and the alkali metal - fullerene interactins.

##### Place, publisher, year, edition, pages
Singapore: World Scientific, 1998
##### Keywords
Fullerenes, C60, X-ray diffraction, single crystal polymer, structure, orthorhombic, chain orientation, alkali metal doping, pressure-temperature phase diagram
##### National Category
Condensed Matter Physics
Physics
##### Identifiers
urn:nbn:se:umu:diva-23483 (URN)978-981-02-3261-0 (ISBN)
##### Note
Editors: Hans Kuzmany, Jörg Fink, Michael Mehring and Siegmar Roth.Available from: 2009-06-20 Created: 2009-06-20 Last updated: 2018-06-08
Sundqvist, B., Edlund, U., Jacobsson, P., Johnels, D., Jun, J., Launois, P., . . . Wågberg, T. (1998). Structural and physical properties of pressure polymerized C60. In: Carbon, vol. 36 issue 5-6: Proceedings of Symposium A: Fullerenes and Carbon Based Materials, of the Joint Meeting of the European Materials Research Society (E-MRS'97) and the International Conference on Advanced Materials (ICAM'97), Strasbourg 1997. Paper presented at the International Conference on Advanced Materials (ICAM'97), Strasbourg 1997 (pp. 657-660). Elsevier B.V.
Open this publication in new window or tab >>Structural and physical properties of pressure polymerized C60
1998 (English)In: Carbon, vol. 36 issue 5-6: Proceedings of Symposium A: Fullerenes and Carbon Based Materials, of the Joint Meeting of the European Materials Research Society (E-MRS'97) and the International Conference on Advanced Materials (ICAM'97), Strasbourg 1997, Elsevier B.V. , 1998, p. 657-660Conference paper, Published paper (Refereed)
##### Abstract [en]

We discuss the structural and dynamic properties of C60 polymerized under low-P, low-T conditions, and suggest that the disordered mixed orthorhombic-tetragonal-rhombohedral phases produced under these conditions arise from nucleation of molecular chains in random directions because of the quasi-free molecular rotation under standard reaction conditions in the fcc phase of C60. Polymerization in He gives results qualitatively different from those obtained in other media.

##### Place, publisher, year, edition, pages
Elsevier B.V., 1998
##### Series
Carbon, ISSN 0008-6223 ; Vol. 36, issues 5-6
##### Keywords
Fullerenes, C60, hydrostatic pressure, high pressure, polymerization, structure, disorder
##### National Category
Condensed Matter Physics
Physics
##### Identifiers
urn:nbn:se:umu:diva-23456 (URN)10.1016/S0008-6223(98)00063-3 (DOI)
##### Conference
the International Conference on Advanced Materials (ICAM'97), Strasbourg 1997
##### Note

Editors: Hans Kuzmany and Pierre Delhaes. Also reprinted in the Proceedings volume Fullerenes and Carbon Based Materials, E-MRS Symposia Proceedings Volume 68, Elsevier 1998, ISBN 0-444-20512-8, with the same Editors and page numbers.

Available from: 2009-06-17 Created: 2009-06-17 Last updated: 2018-06-08Bibliographically approved
Wågberg, T., Persson, P.-A., Sundqvist, B. & Jacobsson, P. (1997). A Raman study of polymerised C60. Applied Physics A: Materials Science & Processing, 64(3), 223-226
Open this publication in new window or tab >>A Raman study of polymerised C60
1997 (English)In: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 64, no 3, p. 223-226Article in journal (Refereed) Published
##### Abstract [en]

Results of Raman scattering studies on high pressure polymerized and photo polymerized C60 are reported. Although prepared according to different routes the Raman spectra of the two polymeric phases of C60 show a quantitative agreement with respect to mode positions and intensity. We conclude from this that both materials have the same structure at least in the short range order, i.e. the same type of bonding and co-ordination between neighbouring C60 molecules. An investigation of the time dependence of the thermal decomposition of high pressure polymerised C60 is also presented. The rate of decomposition of the polymeric phase is found to be multi-exponential at all temperatures investigated. From an Arrhenius-type analysis of the short time data and the long time data, respectively, the activation energy for thermal dissociation of polymeric bonds was found to increase with time.

##### Keywords
Fullerenes, C60, Raman spectroscopy, polymeric fullerenes, fullerene polymers, linear molecular chains, orthorhombic structure, activation energy, polymer breakdown, photopolymer, high pressure synthesis
##### National Category
Condensed Matter Physics
Physics
##### Identifiers
urn:nbn:se:umu:diva-25675 (URN)10.1007/s003390050470 (DOI)
##### Note
Invited paper in Special Issue "Polymeric fullerenes", guest editor Hans KuzmanyAvailable from: 2009-08-28 Created: 2009-08-28 Last updated: 2018-06-08
Moret, R., Launois, P., Persson, P.-A. & Sundqvist, B. (1997). First X-ray diffraction analysis of pressure polymerized C60 single crystals. Europhysics letters, 40(1), 55-60
Open this publication in new window or tab >>First X-ray diffraction analysis of pressure polymerized C60 single crystals
1997 (English)In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 40, no 1, p. 55-60Article in journal (Refereed) Published
##### Abstract [en]

It is shown that C60 single crystals can be polymerized under relatively modest pressure-temperature conditions. The resulting single crystals exhibit long-range order and they are made up of 12 orientation variants. The structure is orthorhombic with a short intermolecular distance along the chains (9.14 Å), characteristic of covalent bonding. We propose a structural mechanism for the polymerization of fullerene-based compounds; it involves a shift of one of the (111) cubic planes together with a shortening of the (111) spacing. The configuration of the polymer chains presents interesting relations with that found in the A1C60 polymer compounds.

##### Keywords
Fullerenes, C60, high pressure synthesis, structure, X-ray diffraction, XRD, molecular chains, intermolecular bonds, cycloaddition, orthorhombic, rotational angles, variants, polymerization mechanism
##### National Category
Condensed Matter Physics
Physics
##### Identifiers
urn:nbn:se:umu:diva-25728 (URN)10.1209/epl/i1997-00424-4 (DOI)
Available from: 2009-09-01 Created: 2009-09-01 Last updated: 2018-06-08
Wågberg, T., Persson, P.-A., Sundqvist, B. & Jacobsson, P. (1997). Polymeric phases of C60. In: Fullerenes: Recent Advances in the Chemistry and Physics of Fullerenes and Related Materials, vol. 5: Proceedings of the 192nd Meeting of the Electrochemical Society, Paris 1997; Symposium Fullerenes: Chemistry, Physics, and New Directions (pp. 674-679). Pennington, NJ: The Electrochemical Society
Open this publication in new window or tab >>Polymeric phases of C60
1997 (English)In: Fullerenes: Recent Advances in the Chemistry and Physics of Fullerenes and Related Materials, vol. 5: Proceedings of the 192nd Meeting of the Electrochemical Society, Paris 1997; Symposium Fullerenes: Chemistry, Physics, and New Directions, Pennington, NJ: The Electrochemical Society , 1997, p. 674-679Conference paper, Published paper (Refereed)
##### Abstract [en]

We have investigated the "low" pressure region where C60 can be transformed into polymeric chains or clusters. To learn more about the polymerization process we have treated pristine C60 at several different temperatures under hydrostatic pressures in silicone oil. We found that the reaction rate varied with temperature. Above 520 K at 1.0 GPa similar and high polymer fractions were obtained in all samples, but at 497 K the polymer fraction was only 10% after three hours, as indicated by the shift of the intensity of the pentagonal pinch mode in the Raman spectrum. Also, samples treated at the same pressure and temperature but with different thermal pre-history showed different degrees of polymerization. We have also found a correlation between the shift of the pentagonal pinch mode in the Raman spectrum to 1463 /cm and the intermolecular vibrational mode at 97 /cm. We therefore make the conclusion that the shift of the pentagonal pinch mode to 1463 /cm corresponds to the presence of dimers in the sample.

##### Place, publisher, year, edition, pages
Pennington, NJ: The Electrochemical Society, 1997
##### Series
Electrochemical Society Proceedings ; 97-42
##### Keywords
Fullerenes, C60, high pressure synthesis, polymerization, polymer chains, dimers, Raman spectroscopy, Raman spectra
##### National Category
Condensed Matter Physics
Physics
##### Identifiers
urn:nbn:se:umu:diva-25838 (URN)1-56677-192-7 (ISBN)
Available from: 2009-09-07 Created: 2009-09-07 Last updated: 2018-06-08

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