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Title: Exotic forms of matter created by interactions with free-electron lasers
Author: Banks, Henry Isaac Bryan
ISNI:       0000 0004 7660 9031
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2019
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In this thesis, we investigate the formation of atomic and molecular states with mul- tiple core electrons missing. These multiple-core-hole (MCH) states are of interest due to their sensitivity to their chemical environment. These MCH states are formed by successive single-photon ionisations of core electrons. This can be achieved by x-ray photons and a sufficiently large intensity such that the photo-ionisation rate competes with the Auger decay rate of core-hole states. To understand the pathways that lead to the formation of MCH states, we study the interaction of free-electron laser (FEL) pulses with atoms and molecules. These lasers are capable of producing short, high-intensity pulses with high photon en- ergy, which make them ideal for forming MCH states. In order to understand the interaction of an FEL with an atom or molecule, we model these interactions com- putationally. We construct rate equations and track how the population of an atom or molecule transitions between different states. These rate equations involve single- photon ionization processes and Auger transitions. To account for these processes, we compute photo-ionisation cross-sections and Auger decay rates. We develop a computational model that allows us to calculate the ion yields produced when an atom or molecule interacts with an FEL pulse. Further, by calcu- lating how the population transitions via different pathways of intermediate atomic and molecular states, we determine the proportion of the population which accesses MCH states. We also compute electron spectra, which provide measurable observ- ables indicating the formation of MCH states.
Supervisor: Emmanouilidou, A. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available