Combining X-ray free electron laser probes of chemical dynamics

Abstract

The development of ultrafast laser sources capable of generating extreme ultraviolet (XUV) and X-ray photons has significantly advanced the study of photochemical processes. This thesis investigates the use of Free Electron Lasers (FELs) as powerful probes for time-resolved spectroscopy, enabling detailed examination of molecular dynamics. Additionally, an experiment utilising a high harmonic generation source (HHG) is also described in this thesis. This provides a comparison and an overview of how the two sources can be used to complement one another. The focus of the experimental work is on 2- and 3-iodothiophene. Ultraviolet (UV) excitation within the 220–300 nm range populates either ππ∗ states localized on the thiophene ring or (n/π)σ∗ states on the C-I bond, both leading to C-I bond dissociation. The iodine fragment was observed to form via competing dissociation pathways, consistent with earlier studies. Direct (n/π)σ∗ excitation results in prompt dissociation, while initial population of the ππ∗ state leads to slower, potentially delayed fragmentation. By harnessing FEL and HHG radiation, the post-excitation dynamics of iodothiophene were probed through various techniques. Each method offers unique insights, collectively providing a comprehensive understanding of the underlying photodissociation dynamics.

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Identifiers

ORCID for Russell Minns: orcid.org/0000-0001-6775-2977

ORCID for Guy Denuault: orcid.org/0000-0002-8630-9492

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