Ultrafast spectroscopy of relativistic processes

Taking pictures of fast moving objects requires short pulses of light: instead of opening and closing a camera shutter at speeds beyond their mechanical capability, photographers in the 1960s hit on the idea of leaving their cameras `open' in a dark room. They would then switch the lights on and off at the moment that, say, a bullet passed in front of the camera, allowing them to capture a still image of a fast moving object.

Similar schemes are used every day in physics labs: with recent improvements in laser technology, experimentalists are routinely able to generate laser pulses which are mere attoseconds (1 as =10^-18s) in duration. This has facilitated several incredible experiments which have been able to `photograph' (or even `video') electron dynamics which evolve on the attosecond scale.

One exciting application of these techologogies has been to probe the evolution of atomic systems driven by 'weird' quantum effects: correlated electron-hole dynamics for instance. As metrological techniques have become more and more sensitive, it has been possible even to elucidate more subtle quantum effects such as spin-orbit coupling which causes splitting of atomic states and associated dynamics. As far back as 2011, experimentalists were able to resolve the attosecond-scale interference effect between two spin-orbit split states in Krypton. Unfortunately, as the experimental techniques have marched onwards, theoretical treatments have lagged behind. However, now with recent developments made at Queen's, we are finally able to support and even lead experiment with our world-leading computer code for modelling laser-atom dynamics: RMT.

The purpose of this project will be to use newly developed capability in the RMT code to address state-of-the-art experimental schemes for atto-scale dynamics in atoms, ions and perhaps even molecules. Recent capability expansions now allow us to model arbitrarily polarised laser pulses and, importantly for this project, relativistic effects in the description of the atomic structure and dynamics. No other method exists to address these problems so we are in a unique position to lead the field.