What is attosecond theory?
An attosecond is 10-18 seconds, or 0.0000000000000000001 seconds. These timescales are so small they are in fact comparible to the timescales of electron motion. So how can we access such small periods of time? Well, one method of probing matter on these timescales, and also with sub angstrom (that's 10-10 metres), is high harmonic generation, which is a phenomenon that occurs when atoms, molecules, clusters, or solids, are exposed to high intensity coherent radiation. These methods are bringing us closer to the dream of watching a complex chemical reaction in real time, and will bring answers to fundamental questions in many disciplines, such as chemistry, biology and condensed matter physics. As a comparison, femtochemistry revolutionised our understanding of the making, and breaking, of chemical bonds. For an overview see this excellent Attosecond Physics review.
The laser intensities we model are typically in the region of 1014 W/cm2, as this allows relativistic effects to be neglected and the dipole approximation to be made. Other phenomena that may occur, and which are also investigated by our group at University College London, include above threshold ionisation and non-sequential double ionisation.
My research has focussed mainly on the development of analytical models to describe high harmonic generation in homonuclear and heteronuclear diatomic molecules, as well as pursuing more numerical approaches , such as using time dependent density functional theory, and more recenlty, the exciting new technique known as the Coupled Coherent State (CCS) method. The CCS method is a revolutionary technique that has only very recently been used to model strong field physics, and will bring us a more comlpete physical understanding of mechanisms that give rise to, as of yet, poorly understood phenomena, such as harmonic resonance.