Novel approaches to theoretical and numerical calculations of experimental observables in intense laser-atom interactions

Thesis

The interaction of laser light with atoms has attracted a lot of attention over the years due to the questions it raises from the point of view of fundamental physics, but also due to the practical applications in which it is a core part. If the laser pulse is very intense, it can induce the excitation or ionisation of one or more electrons from the target. This opens up a plethora of physics phenomena to study and analyse.

In this thesis, the ionisation of noble-gas atoms is subject to numerical and theoretical investigations. Initially motivated by the potential of this interaction-scenario to be a method to place bounds on the peak-intensity of a laser beam-pulse, the ionisation of atomic xenon illuminated by extreme such pulses of light is firstly analysed by means of state-of-the-art field-ionisation-rates formulae, with care being taken that the simulation-setup respects the stringent experimental constraints which are found in a real target chamber. Then considerations about the time-dependent-Schrödinger-equation (TDSE) are presented, which showcase both the theory and the implementation of a fully-distributed numerical solver for very accurate studies on the laser-atom interaction. This has been used to carry out numerical simulations: specifically, the differences between the dipole-approximated and the beyond-dipole-approximation quantum-dynamics of ionisation are analysed for a hydrogenic-atom target. Then, the multi-electron nature of argon is taken into consideration from the point of view of a mean-field approach: the time-dependent-density-functional-theory (TDDFT). In the Kohn-Sham formalism, this reduces the problem to propagating in time nine coupled one-electron TDSE’s, making it amendable to numerical studies performed in reasonable wall-clock times. Finally, conclusions are drawn and possible further work arising from the ideas discussed is proposed and analysed.

Authors: Ouatu, I

• DOI: 10.5287/ora-y0rz440wg
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English