Dissociative ionisation of the hydrogen molecular ion in intense laser fields

Abstract

The hydrogen molecular ion represents the simplest molecule in which correlations between electronic and ionic motion can be studied quantum mechanically. Understanding the interplay between electronic and ionic motion is fundamental in a wide range of areas such as the design of electronic devices, probes and sensors, and in the areas of condensed matter and plasma physics, medicine and biochemistry. Of particular importance is the interaction with attosecond laser pulses since this opens up the possibility of steering electron dynamics in order to control chemical reactions. Studying the interaction between the hydrogen molecular ion and ultrashort VUV pulses therefore provides important insights into how these pulses interact with more complex molecules. This thesis is dedicated to the description of the interaction of the H₂⁺ exposed to intense ultra-short laser pulses through the development of two massively parallel codes that efficiently solves the time-dependent Schrödinger equation (TDSE) in full dimensionality using a non-Born-Oppenheimer Hamiltonian that treats electronic and nuclear motion on an equal footing. The codes treat the electronic coordinate in cylindrical coordinates in 2D and in Cartesian coordinates in 3D. This allows us to describe parallel and arbitrary orientations between the molecular axis and the z-axis respectively. In addition, a parallel library for calculating the photoelectron spectra using three different methods has also been developed. The methods implemented in the library are the time dependent surface flux method (t-SURFF), the sampling point method and the Fourier transform of the spatial wavefunction into momentum space. The library has been written to be as portable as possible and can be interfaced straightforwardly with other codes that are used for modelling laser-matter interactions, such as the codes developed in this thesis, together with other codes that solve the Kohn-Sham equations of the time-dependent density functional theory (TDDFT).