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Title: Numerical methods for the interaction of atoms with intense low frequency laser pulses
Author: Pyke, Dean Thomas
ISNI:       0000 0004 8498 8449
Awarding Body: Royal Holloway, University of London
Current Institution: Royal Holloway, University of London
Date of Award: 2016
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In recent years intense laser fields have become more available over a frequency range extending from the infrared to the ultraviolet in the form of short pulses. In the low frequency regime where the photon energy is much lower than the ionisation potential, the advent of high intensity lasers has allowed detailed investigation into phenomena such as above threshold ionisation (ATI), high order harmonic generation (HHG) and attosecond pulse generation. The numerical integration of the time dependent Schrödinger equation (TDSE) has become the main theoretical approach for the quantitative study of laser-atom interaction and investigation of these short pulses of very high intensity makes this method unavoidable if accurate results are required. In this thesis we begin by examining fundamental features of the dynamics of an atom when interacting with an intense electromagnetic field, looking at the description of the field, the Hamiltonian and mechanisms of ionisation. We then investigate the numerical solution of the TDSE, looking at different methods of representation of the wave function and analyse different time propagation algorithms. We then present the results of our programs using one dimensional model potentials in a wide range of laser parameters. We investigate new methods to calculate observables; such as the time dependent surface flux method combined with exterior complex scaling. We vary the frequency, intensity, pulse length and carrier phase of the laser, studying how these parameters affect observables including the ATI spectrum. Finally we extend our program to the full three dimensional atom, again over a range of laser parameters and discuss the computational difficulties for intense low frequency laser pulses. We use these programs to try to understand the low energy structure (LES) found in recent experiments for intense low frequency pulses.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Ionisation ; Frequency ; Laser ; Numerical ; Propagation ; Intense ; Fields