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| 2. |
- Kukk, E., et al.
(författare)
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Internal energy dependence in x-ray-induced molecular fragmentation : An experimental and theoretical study of thiophene
- 2015
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 91:4
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Tidskriftsartikel (refereegranskat)abstract
- A detailed experimental and theoretical investigation of the dynamics leading to fragmentation of doubly ionized molecular thiophene is presented. Dissociation of double-ionized molecules was induced by S 2p core photoionization and the ionic fragments were detected in coincidence with Auger electrons from the core-hole decay. Rich molecular dynamics was observed in electron-ion-ion coincidence maps exhibiting ring breaks accompanied by hydrogen losses and/or migration. The probabilities of various dissociation channels were seen to be very sensitive to the internal energy of the molecule. Theoretical simulations were performed by using the semiempirical self-consistent charge-density-functional tight-binding method. By running thousands of these simulations, the initial conditions encountered in the experiment were properly taken into account, including the systematic dependencies on the internal (thermal) energy. This systematic approach, not affordable with first-principle methods, provides a good overall description of the complex molecular dynamics observed in the experiment and shows good promise for applicability to larger molecules or clusters, thus opening the door to systematic investigations of complex dynamical processes occurring in radiation damage.
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| 3. |
- Kukk, E., et al.
(författare)
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Molecular dynamics of photodissociation : towards more complex systems
- 2015
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Ingår i: XXIX INTERNATIONAL CONFERENCE ON PHOTONIC, ELECTRONIC, AND ATOMIC COLLISIONS (ICPEAC2015), PTS 1-12. - : Institute of Physics Publishing (IOPP).
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Konferensbidrag (refereegranskat)abstract
- We present a combined experimental and theoretical study of the photodissociation of thiophene molecule using energy-resolved electron-ion-ion coincidence technique and self-consistent charge density functional tight-binding theory combined with a statistical approach. The observed complex molecular dynamics with many internal-energy-dependent fragmentation pathways is successfully described by the theoretical simulations.
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| 4. |
- Kukk, E., et al.
(författare)
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Photoelectron recoil in CO in the x-ray region up to 7 keV
- 2017
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Ingår i: PHYSICAL REVIEW A. - 2469-9926. ; 95:4
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Tidskriftsartikel (refereegranskat)abstract
- Carbon 1s photoelectron spectra of CO molecules in gas phase were recorded in the tender x-ray energy range, from 2.3 to 6.9 keV. The intensity ratios of individual peaks from nu = 0 to 3 within the vibrational progression of the C 1s photoelectron spectrum were determined at the various photon energies and are shown to be strongly affected by the photoelectron recoil effect. The experimental vibrational intensity ratios are compared with theoretical predictions at different levels of accuracy. Developments of the recoil model, using generalized Franck-Condon factors, rovibrational coupling, Morse potential energy curves, and accurate angular averaging are presented and applied to the analysis of the experimental results.
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| 5. |
- Laksman, J., et al.
(författare)
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Dissociation Pathways in the Cysteine Dication after Site-Selective Core Ionization
- 2014
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 118:40, s. 11688-11695
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Tidskriftsartikel (refereegranskat)abstract
- A photoelectronionion coincidence experiment has been carried out on the amino acid molecule cysteine after core-ionization of the O 1s, N 1s, C 1s, and S 2p orbitals. A number of different dissociation channels have been identified. Some of them show strong site-selective dependence that can be attributed to a combination of nuclear motion in the core-ionized state and Auger processes that populate different final electronic states in the dication.
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| 6. |
- Levola, H., et al.
(författare)
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Fragmentation of thymidine induced by ultraviolet photoionization and thermal degradation
- 2013
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Ingår i: International Journal of Mass Spectrometry. - : Elsevier BV. - 1387-3806 .- 1873-2798. ; 353, s. 7-11
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Tidskriftsartikel (refereegranskat)abstract
- Fragmentation of gas phase thymidine at different temperatures was studied with vacuum ultraviolet radiation and time-of-flight spectroscopy. Partial ion yield measurements were carried out in order to study the appearance energies of thymidine and its main fragments. The appearance energies of thymidine and its deoxyribose- and thymine-based fragments were determined to be 8.39, 8.77 and 8.81 eV, independently of temperature. The thermal decomposition of the sample was observed to start around 138-139 C and it was explained by the breakage of the glycosidic bond, accompanied by hydrogen transfer from the deoxyribose ring to the thymine base.
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