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Title: New instrumentation and methods for ultrafast pump-probe spectroscopy
Author: Walke, Daniel John
ISNI:       0000 0004 6346 9981
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2017
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Recent advances have led to the demonstration of trains of attosecond pulses and isolated attosecond pulses in the vacuum ultraviolet (VUV) and extreme ultraviolet (XUV) regions of the electromagnetic spectrum in a number of laboratories. This has raised the possibility of direct time resolved measurements of correlation driven electron dynamics within molecules, with a long term aim of unprecedented control over the dynamics of matter at atomic and molecular length scales. Particular interest has arisen towards the possibility of a charge migration mechanism within molecules, in which purely electron driven processes result in the movement of charge around an excited molecule in the absence of any nuclear dynamics. However, even once these sources have been established, using them in time resolved experiments is challenging. This is due to extremely short time-scales involved, the complexity of the processes under study, and the limitations of currently available attosecond sources. In this thesis I describe the development of novel instrumentation and methods for attosecond pump – probe experiments on electron dynamics in molecules. Strategies for the experimental study of charge migration are reviewed in detail which motivates the design and implementation of a purpose built instrument combining an electron velocity map imaging (VMI) spectrometer and an ion time of flight (iTOF) spectrometer. This instrument is designed in tandem with the development and characterisation of an isolated pulse at the new photon energy of 20eV. This 20eV pulse is intrinsically synchronized with another attosecond pulse at 90eV. Together, the new instrument and light source represent a unique capability for the investigation of electron dynamics in molecules. Finally, the first experimental results are presented and perspectives for future studies using the new developments are discussed.
Supervisor: Tisch, John W. G. ; Frasinski, Leszek J. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral