Extending high harmonic generation spectroscopy to new molecular species
File(s)
Author(s)
McGrath, Felicity
Type
Thesis or dissertation
Abstract
HHG spectroscopy is a powerful tool for observing electronic structure along with
electronic and nuclear dynamics with state of the art resolution on the attosecond
(10^−18 s = 1 as) timescale and angstrom (10^−10 m = 1 °A). Thus far, HHG spectroscopy
has been applied to small hydrocarbons such as ethylene and methane using
an 800 nm drive laser field wherein dynamics can only be measured in a 0.9 − 1.6 fs
time window. This PhD has two primary aims: 1) to extend the time window over
which we can make measurement up to 4 fs using an 2 μm drive laser field and
2) to perform HHG spectroscopy on molecules which are in the liquid phase at room
temperature. The molecules at the focus of this thesis are benzene and substituted
benzenes. The design and development of an apparatus to generate a stable vapour
jet from a thin continuous nozzle is presented. The completed and tested apparatus
has demonstrated that stable and reproducible spectra can be acquired with no
contamination between different samples as they are switched over. Comparison of
methylated benzene to benzene harmonic spectra show good agreement with theoretical
results on coupled electron-nuclear dynamics developed by our collaborators.
We also compare HHG spectra acquired under similar generating conditions from
deuterated and protonated benzene which enables us to track nuclear dynamics and
to determine the origin of the ionized electron in benzene. HHG spectra from the
halogenated benzenes, in particular fluorobenzene, seem to illustrate the contribution
of more tightly bound orbitals to the HHG signal which is indicative of dynamical
interferences.
electronic and nuclear dynamics with state of the art resolution on the attosecond
(10^−18 s = 1 as) timescale and angstrom (10^−10 m = 1 °A). Thus far, HHG spectroscopy
has been applied to small hydrocarbons such as ethylene and methane using
an 800 nm drive laser field wherein dynamics can only be measured in a 0.9 − 1.6 fs
time window. This PhD has two primary aims: 1) to extend the time window over
which we can make measurement up to 4 fs using an 2 μm drive laser field and
2) to perform HHG spectroscopy on molecules which are in the liquid phase at room
temperature. The molecules at the focus of this thesis are benzene and substituted
benzenes. The design and development of an apparatus to generate a stable vapour
jet from a thin continuous nozzle is presented. The completed and tested apparatus
has demonstrated that stable and reproducible spectra can be acquired with no
contamination between different samples as they are switched over. Comparison of
methylated benzene to benzene harmonic spectra show good agreement with theoretical
results on coupled electron-nuclear dynamics developed by our collaborators.
We also compare HHG spectra acquired under similar generating conditions from
deuterated and protonated benzene which enables us to track nuclear dynamics and
to determine the origin of the ionized electron in benzene. HHG spectra from the
halogenated benzenes, in particular fluorobenzene, seem to illustrate the contribution
of more tightly bound orbitals to the HHG signal which is indicative of dynamical
interferences.
Version
Open Access
Date Issued
2015-06
Online Publication Date
2016-04-30T06:00:13Z
2016-05-06T09:14:35Z
Date Awarded
2015-11
Advisor
Marangos, Jon
Tisch, John
Sponsor
Engineering and Physical Sciences Research Council
Grant Number
P34541
Publisher Department
Faculty of Natural Sciences
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)