Formation and Decay of Multiply-Charged Molecules upon Single-Photon Excitation
Abstract
This thesis presents the investigation of dissociative multi-ionisation processes in gas-phase molecules through single photon absorption, employing a combination of ion spectrometry and electron spectroscopy, relying on a magnetic bottle time-of-flight principle. This method is pivotal for capturing all electrons emitted during ionisation, enabled by its unique electric and magnetic field configuration.
The initial part of the thesis (Paper I) explores Coulomb explosion in CD3I, induced by deep inner-shell ionisation with hard X-rays. The study examines core vacancy relaxation through Auger-Meitner cascades. Using a a comparatively simple model, the relaxation and subsequent dynamics of Coulomb explosions are simulated, yielding results that align well with experimental data for medium charge states, although limitations are noted for higher charge states. The research provides insights into the distribution of final charge states following L-shell ionisation, including the involvement of rapid Coster-Kronig transitions.
Papers II-V focus on the dissociation mechanisms of small molecules (SO2,
OCS, and HNCS) upon single photon double valence ionisation, employing
the same experimental approach. Paper II discusses an unconventional
dissociation mechanism in SO2 leading to the unexpected charge retaining
SO2+ species via autoionisation of the super-excited 2h-1p Rydberg state
molecular oxygen, O2, in an ionic pathway via a newly revealed metastable state of O-O-S2+. Paper IV examines bond rearrangement upon double ionisation in OCS, establishing a newly identified metastable isomer COS++. Paper V details the dissociation pathways of the main fragmentation channels of HNCS. Each paper contributes to a broader understanding of molecular behaviour under double ionisation.
Paper VI focuses on the sequential three-body dissociation mechanisms leading to unusual shapes, that also deviate from the expected limiting slope of -mB/mBC. Two isomers of perflouro-propyl iodide are found to sequentially break into three fragments, ABC++ → A+ + BC+ followed by BC+ → B+ + C, where simulations suggest that the bow-tie and twisted shapes arise from femtosecond secondary lifetimes. At these short time scales the BC+ is placed well within the effective Coulomb range of A+.
Overall, this thesis sheds light on the complex dynamics of dissociative multi-ionisation in several molecules, paving the way for future research in molecular dynamics and chemical reactions in more complex environments.
Parts of work
1. M. Wallner, J. H. D. Eland, R. J. Squibb, J. Andersson, A. Hult Roos, R. Singh, O. Talaee, D. Koulentianos, M. Novella Piancastelli, M. Simon and R. Feifel. Coulomb explosion of CD3I induced by single photon deep inner-shell ionisation. Scientific Reports, 10, 1246 (2020), https://doi.org/10.1038/s41598-020-58251-9 2. M. Jarraya, M. Wallner, G. Nyman, S. Ben Yaghlane, M. Hochlaf, J. H. D. Eland and R. Feifel. State selective fragmentation of doubly ionized sulphur dioxide. Scientific Reports, 11, 17137 (2021), https://doi.org/10.1038/s41598-021-96405-5 3. M. Wallner, M. Jarraya, E. Olsson, V. Ideböhn, R. J. Squibb, S. Ben Yaghlane, G. Nyman, J. H. D. Eland, R. Feifel and M. Hochlaf. Abiotic molecular oxygen production – Ionic pathway from sulphur dioxide. Science Advances, 8, eabq5411 (2022), https://doi.org/10.1126/sciadv.abq5411 4. M. Jarraya, M. Wallner, S. Ben Yaghlane, E. Olsson, V. Ideböhn, R. J. Squibb, J. Palaudoux, G. Nyman, M. Mogren Al-Mogren, J. H. D. Eland, R. Feifel and M. Hochlaf. Doubly ionized OCS bond rearrangement upon fragmentation – experiment and theory. Physical Chemistry Chemical Physics, 25, 19435-19445 (2023), https://doi.org/10.1039/d3cp01688a 5. M. Wallner, E. Olsson, V. Daver Ideböhn, M. Parriani, R. J. Squibb, S. Lundberg, D. Cole, G. Nyman, J. H. D. Eland, M. Hochlaf and R. Feifel. Double ionisation and fragmentation of HNCS. In manuscript 6. S. Price, M. Wallner, E. Olsson, M. Parkes, V. Daver Ideböhn, M. Parriani, R. J. Squibb, J. H. D. Eland and R. Feifel. Femtosecond lifetimes from island shapes in sequential three- body dissociations. In manuscript
Degree
Doctor of Philosophy
University
University of Gothenburg
Institution
Department of Physics ; Institutionen för fysik
Disputation
Fredagen den 26 april 2024, kl 13:15, PJ-Salen, Institutionen för fysik, Fysikgården 2, Göteborg.
Date of defence
2024-04-26
Date
2024-03-25Author
Wallner, Måns
Keywords
Molecule, electrons, ions, dissociation, fragmentation, coincidence, time of flight, VUV, X-radiation.
Publication type
Doctoral thesis
ISBN
978-91-8069-670-8
Language
eng