Coherent electron dynamics in atoms and small molecules following attosecond photoionisation

This work seeks to predict and understand novel ultrafast dynamics induced and measured by the action of a laser pulse. For this purpose we develop new theory and we make use of several ab-initio numerical methods. In particular, we apply the recently developed technique of restricted correlation space B-spline ADC, which uses B-spline functions to represent both bound and continuum-like electronic states and thereby model dynamics following ionisation. This work has three major components. The first is the development of a new interferometric approach for detecting revivals of an initially-decaying molecular state though the use of an omega / two omega pulse scheme with carefully controlled relative phase. We develop and solve analytically a model system containing a state coupled to a Bixon-Jortner quasicontinuum, obtaining an interferometric signature of revival which is easily generalised to realistic systems. Moreover, we analyse how this revival signature is influenced by the system parameters, and we suggest optimal conditions for its observation. The second and most significant component is the application of ab-initio numerical methods to study the dynamics which follow coherent population of ionisation satellites created by the removal of an inner-valence electron in atoms by an attosecond duration laser pulse. Our calculations show that this kind of system exhibits radial electron density oscillations and, for the specific case of the Argon atom, we study the precise nature of these predicted oscillations. We further illustrate several schemes by which this behaviour might be probed, and we provide initial numerical evidence that the probe is sensitive to the electron dynamics. The final part of the work is a numerical study of Auger decay in a system where the molecular orbital picture of ionisation breaks down, leading to coherent population of a series of decaying states which we predict will exhibit non-exponential decay character.