TY - BOOK

T1 - Filming Femtosecond Molecular Movies with X-ray Pulses

AU - Kjær, Kasper Skov

PY - 2013

Y1 - 2013

N2 - This thesis describes the investigation of time-resolved phenomena using X-raytechniques, and in particular the new possibilities and challenges arising from theapplication of these techniques on the femtosecond time-scale.The thesis will review the processes following laser excitation of molecular speciesin solution, describing the interplay between electronic and structural dynamics, aswell as the role of the solvent. This will be followed by an introduction of the threeX-ray techniques used in this work, and it will be shown how the application of thesetechniques in a laser pump / X-ray probe framework can help elucidate the excitedstate dynamics. The theoretical information content of the X-ray techniques will bediscussed, as well as the practical experimental considerations for their implementation.This is done in order to demonstrate the potential increase in informationcontent yielded by (and the practical challenges connected to) their simultaneous implementationin a single experiment. Finally, the experimental results of a signicantset of laser pump / X-ray probe experiments will be presented and discussed in orderto gauge the applicability of these techniques as tools for characterizing excited statesand excited state dynamics.A central component of the work has been related to the transition from synchrotronbased X-ray sources to X-ray free-electron laser (XFEL) sources. The timeresolutionand ux of the XFEL source is roughly three orders of magnitude betterthan the standardized laser pump / X-ray probe experiment at synchrotron sources.This has necessitated both a systematic experimental investigation, and the formulationof a theoretical framework within which to describe the very inhomogeneousand highly energetic states of the molecular system under investigation and their localsolvent environment on the sub picosecond time-scale from an X-ray perspective.

AB - This thesis describes the investigation of time-resolved phenomena using X-raytechniques, and in particular the new possibilities and challenges arising from theapplication of these techniques on the femtosecond time-scale.The thesis will review the processes following laser excitation of molecular speciesin solution, describing the interplay between electronic and structural dynamics, aswell as the role of the solvent. This will be followed by an introduction of the threeX-ray techniques used in this work, and it will be shown how the application of thesetechniques in a laser pump / X-ray probe framework can help elucidate the excitedstate dynamics. The theoretical information content of the X-ray techniques will bediscussed, as well as the practical experimental considerations for their implementation.This is done in order to demonstrate the potential increase in informationcontent yielded by (and the practical challenges connected to) their simultaneous implementationin a single experiment. Finally, the experimental results of a signicantset of laser pump / X-ray probe experiments will be presented and discussed in orderto gauge the applicability of these techniques as tools for characterizing excited statesand excited state dynamics.A central component of the work has been related to the transition from synchrotronbased X-ray sources to X-ray free-electron laser (XFEL) sources. The timeresolutionand ux of the XFEL source is roughly three orders of magnitude betterthan the standardized laser pump / X-ray probe experiment at synchrotron sources.This has necessitated both a systematic experimental investigation, and the formulationof a theoretical framework within which to describe the very inhomogeneousand highly energetic states of the molecular system under investigation and their localsolvent environment on the sub picosecond time-scale from an X-ray perspective.

UR - https://soeg.kb.dk/permalink/45KBDK_KGL/fbp0ps/alma99122699797605763

M3 - Ph.D. thesis

BT - Filming Femtosecond Molecular Movies with X-ray Pulses

PB - The Niels Bohr Institute, Faculty of Science, University of Copenhagen

ER -