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The study of atomic systems interacting with intense ultra-short light pulses is currently attracting significant attention. These ultra-short pulses have recently opened up the possibility of studying electronic motion within atoms in the time domain. At present, the most advanced theoretical approaches for the description of atoms irradiated by intense few-cycle light fields are approaches dedicated to two-active electron systems. However, very few theoretical approaches are currently available to describe complex multielectron atoms, such as Ne and Ar, irradiated by intense ultra-short light pulses. In order to describe the response of such complex atoms to intense ultra-short light pulses, an approach is needed which can accurately describe both the multielectron atomic structure and the multielectron response to the few-cycle light field. In this presentation, we describe a new ab initio non-perturbative time-dependent R-matrix (TDRM) theory that is capable of describing the multielectron atomic response to intense ultra-short light pulses. To verify the accuracy of our new approach, we have investigated multiphoton ionisation of Ar and Ne irradiated by intense laser fields. Ionisation rates obtained using the current time-dependent approach are in excellent agreement with the most accurate rates available. We have also recently employed the new approach to obtain momentum distributions of electrons emitted when Ne is irradiated by a sequence of two ultra-short pulses. We have compared our results with the results of a simple model which allows us to extract the essential physics involved in these emission processes. |
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