Apparatus design and experimental studies of XUV initiated HHG

Abstract

This thesis presents the work on a new beamline for ultra-fast spectroscopy experiments, along with the study of a new ultra-fast spectroscopy technique for studying attosecond electron dynamics: XUV initiated high harmonic generation (XiHHG) XiHHG is an extension of the high harmonic generation (HHG) technique for ultra-fast spectroscopy. XiHHG replaces the tunnel ionisation in HHG with single photon ionisation, and thus an XUV field is used to ionise the electron and a colinear IR field is used to recombine the electron. A goal of this is that energetically deep levels of atoms and molecules can be probed without the need for a very strong IR field.

The specifications of the new beamline required that it be entirely housed in a vacuum of pressures on the order of 1×10 −6 mbar. As all of the optics and experimental controls were also in vacuum, electronic feed-throughs were implemented and sophisticated data acquistion software was developed. As the nature of the data collected for these experiments is large in volume, significant time was also spent creating an analysis script to handle the data automatically. This enabled the data to be transmitted amongst experimenters with ease and accuracy. Preliminary experimental results are shown from the beamline, with some possible theoretical explanations investigated. Further theoretical work is required in order to fully interpret the experimental results.