X-ray photoelectron spectroscopy measurements of photochemical dynamics using a seeded free electron laser
X-ray photoelectron spectroscopy measurements of photochemical dynamics using a seeded free electron laser
The development of free electron lasers (FELs) as sources of femtosecond duration x-ray pulses has enabled the use of time-resolved x-ray photoelectron spectroscopy (TR-XPS) to study ultrafast excited state molecular dynamics. By utilising the sensitivity of XPS as a probe of the changing environment of core-shell electrons in a time-resolved experiment, information about the local electronic environment of specific atoms within a molecule can be obtained.
The work presented in this thesis investigates how XPS signals, shake-down transitions, and secondary Auger-Meitner emission can be used to measure photochemical processes in experiments on gas phase CS2 & 2-iodothiophene. Leveraging the site-selectivity of core-shell spectroscopy this work demonstrates how the added stability afforded by a seeded FEL, used to generate the probing x-ray, enhances the measurements resolution and effectiveness to capture changes in local environments.
The results provide the first experimental measurements of time-resolved changes in shake-down transitions that report on the character of the excited states involved in the reactions. Specifically, the shake-down transitions provide a new probe of the internal conversion dynamics of CS2, allowing for definitive assignments of the excited states and the branching between singlet and triplet dissociation pathways (Chapter 3). While in 2-iodothiophene the shift in the shake-down energy provides a direct mapping to internuclear separation and can be used as a probe of structural dynamics (Chapter 4). Finally, the potential and challenges of Auger-Meitner measurements are presented in a second study of the photodissociation reactions of CS2 (Chapter 5).
X-ray, free electron lasers, Time-resolved photoelectron spectroscopy, Core-shell electron spectroscopy, seeded free electron laser, x-ray photoelectron spectroscopy (xps), molecular dynamcis, photochemistry, pump-probe, Photodissociation
University of Southampton
Thompson, Henry James
2656b8de-fb3f-4702-bb49-a60a3f837d1d
2026
Thompson, Henry James
2656b8de-fb3f-4702-bb49-a60a3f837d1d
Minns, Russell
85280db4-c5a6-4a4c-82fe-75693c6a6045
Woodhouse, Jo
94d6c235-3e1e-44bc-8379-525862fd382c
Thompson, Henry James
(2026)
X-ray photoelectron spectroscopy measurements of photochemical dynamics using a seeded free electron laser.
University of Southampton, Doctoral Thesis, 139pp.
Record type:
Thesis
(Doctoral)
Abstract
The development of free electron lasers (FELs) as sources of femtosecond duration x-ray pulses has enabled the use of time-resolved x-ray photoelectron spectroscopy (TR-XPS) to study ultrafast excited state molecular dynamics. By utilising the sensitivity of XPS as a probe of the changing environment of core-shell electrons in a time-resolved experiment, information about the local electronic environment of specific atoms within a molecule can be obtained.
The work presented in this thesis investigates how XPS signals, shake-down transitions, and secondary Auger-Meitner emission can be used to measure photochemical processes in experiments on gas phase CS2 & 2-iodothiophene. Leveraging the site-selectivity of core-shell spectroscopy this work demonstrates how the added stability afforded by a seeded FEL, used to generate the probing x-ray, enhances the measurements resolution and effectiveness to capture changes in local environments.
The results provide the first experimental measurements of time-resolved changes in shake-down transitions that report on the character of the excited states involved in the reactions. Specifically, the shake-down transitions provide a new probe of the internal conversion dynamics of CS2, allowing for definitive assignments of the excited states and the branching between singlet and triplet dissociation pathways (Chapter 3). While in 2-iodothiophene the shift in the shake-down energy provides a direct mapping to internuclear separation and can be used as a probe of structural dynamics (Chapter 4). Finally, the potential and challenges of Auger-Meitner measurements are presented in a second study of the photodissociation reactions of CS2 (Chapter 5).
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Published date: 2026
Keywords:
X-ray, free electron lasers, Time-resolved photoelectron spectroscopy, Core-shell electron spectroscopy, seeded free electron laser, x-ray photoelectron spectroscopy (xps), molecular dynamcis, photochemistry, pump-probe, Photodissociation
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Local EPrints ID: 512700
URI: https://eprints.soton.ac.uk/id/eprint/512700
PURE UUID: 1d847ba9-12c8-4739-87ed-e71770ae1c4f
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Date deposited: 17 Jul 2026 16:41
Last modified: 13 Sep 2026 15:49
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Author:
Henry James Thompson
Thesis advisor:
Jo Woodhouse
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