研究目的

Solving the semi-relativistic, time-dependent Schr?dinger equation for general, multi-electron atoms and molecules in intense, ultrashort, arbitrarily polarized laser pulses.

研究成果

The RMT method has been applied to many cutting-edge problems in strong-field physics, including the experimentally relevant techniques of HHG, ATAS and strong-field rescattering. On the molecular side several ab initio approaches have been implemented to describe interaction with strong fields, with the molecular R-matrix Floquet approach one of the first methods applicable to multi-electron systems. The implementation was limited to diatomic molecules and monochromatic (i.e. long) fields. Subsequently several different approaches were developed including the haCC method of Majety and Scrinzi that has been applied to diatomic and triatomic molecules, the Spanner-Patchkovskii approach with approximate exchange applicable to small and medium-sized molecules and the B-Spline Algebraic Diagrammatic Construction (ADC) of Averbukh and Ruberti. Recently, the XChem quantum chemistry package has been extended to support calculations of field-ionization of small molecules (and atoms). For the smallest molecules like H2 a near full quantum (including nuclear motion) treatment in perturbative fields has been developed. In larger molecules (e.g. CH4) interacting with strong fields, the coupled electronic-nuclear problem can be solved using the multiconfigurational strong-field approximation with Gaussian nuclear wavepackets method.

研究不足

The description of the atomic/molecular structure is provided from other, time-independent R-matrix codes, and the capabilities (in terms of structure) are, in some sense, inherited therefrom. Thus, the atomic calculations can optionally include Breit-Pauli relativistic corrections to the Hamiltonian, in order to account for the spin-orbit effect. However, no such capability exists for the molecular case. Furthermore, the fixed-nuclei approximation is adopted in the molecular calculations (so nuclear motion is neglected). Similarly, all calculations are restricted to the description of a single electron in the outer region, and consequently the study of double-ionization phenomena is not yet within the capabilities of the method. Finally, the parallel strategy employed necessitates the use of at least two (and usually many more) computer cores. As a result, there is no option for serial calculations and, for most realistic cases, a massively parallel architecture (several hundred cores) will be required.