Since my appointment at UCL, the ultimate goal of my research was to model, understand and steer correlated multielectron dynamics in intense laser fields. As much as possible, we have sought orbit- based analytical or semi-analytical models as they are intuitive, transparent, and allow particular features to be switched on and off at will. Furthermore, they are numerically inexpensive and thus suitable to more complex systems.
Thereby, we have adopted a two-pronged strategy:
Substantially modifying more established approaches, such as the strong-field approximation (SFA), in order to incorporate electron-electron correlation, excitation and the influence of residual binding potentials.
Developing alternative approaches or bringing methods from other areas of knowledge to strong-field physics. These methods were then tested in simple models, and, if successful, the complexity of the
problem was increased.
One should note that the SFA, which is the most widespread analytic approach in strong-field physics, exhibits severe limitations, which become critical near the ionization threshold and for extended systems such as molecules. These include: (i) neglecting the residual binding potential when the electrons are in the continuum; (ii) neglecting the influence of the field when the electrons are bound; (iii) considering the core to be static. There are currently pressing needs to overcome these limitations, due to worldwide experimental evidence that the core dynamics are important. Due to their extreme difficulty, including branch cuts and chaotic behaviour near the core, only a handful of groups worldwide has succeeded in developing analytic approaches beyond the SFA, including my group at UCL. As applications, we have focused on subfemtosecond imaging, steering electron dynamics, and
on quantum interference effects.
Group picture in March 2020 (during the pandemic). From top left, clockwise: Cornelia Hofmann, Abbie Bray, Andy Maxwell, Tobin Holtmann, Heloise Chomet and Carla Faria
This vision has been supported by three main grants: the EPSRC Advanced Fellowship “Alternative S-Matrix Approaches for Matter in Strong Laser Fields”, from 2006 to 2011, and, subsequently, by the EPSRC grants "Orbit-Based Methods for Multielectron Systems in Strong Fields” and "AQuaDiP: Advanced Quantum Approaches to Double Ionization Processes" . Several smaller grants, post-doctoral positions and studentships have been fitted around these awards. It has led to the reseaarch lines below.