Development and application of time-dependent R-matrix theory for the multi-electron dynamics of atoms in ultra-short light pulses

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We aim to develop the theory and associated computer programsto describe the time-dependent dynamics of a general atom in anultra-short, intense laser pulse. Current technology allows the creationof light pulses that are comparable in duration to the time it takesan electron to orbit an atom. By subjecting atoms to these shortpulses, it may be possible to adjust the electronic motion and henceto control the atom to an unprecedented degree.We aim to develop a theory that can be used to accurately predict theresponse of the entire multi-electron atom. To do so, we combinea multi-electron atomic theory, such as the R-matrix theory, withtime-dependent numerical techniques to obtain a novel approach for thedescription of atoms: the time-dependent R-matrix theory. We will developa substantial, new, computational program, containing several thousandsof lines of code, which exploits existing programs, developed by theapplicants, and which builds on our expertise in developing new programsas a world-leading group in theoretical atomic physics. This program willrequire significant computational resources, and the codes to be developedwill thus be developed for mid-range parallel computers.Initial investigations will be focussed on the noble-gas atoms from Neonwards, since these are the atoms most often used in state-of-the-artshort-pulse experiments. However, these atoms can only be studiedtheoretically with proper accuracy through explicit multi-electron techniques,such as the ones in the proposed method. By comparing results obtainedby the time-dependent R-matrix program with results obtained by thetime-independent R-matrix Floquet program, we will furthermore developunique insight into the detailed atomic dynamics in strong laser fields.Following the initial investigation of the behaviour of atoms in ultra-short pulses,we will continue the development of the codes towards the investigation ofprocesses in which two electrons are ejected. These processes will be ofincreasing interest in the coming years due to new free-electron laser facilities,which will provide high-intensity X-ray radiation. When atoms are subjected tosuch radiation, several electrons can be emitted simultaneously. The developmentof a computer code capable of describing double ionization of general atoms inintense light fields will thus provide a massive boost to all research exploiting thesenew X-ray radiation facilities.