R-matrix Floquet theory of molecular multiphoton processes

A unified R-matrix Floquet theory of multiphoton processes is introduced which can be used to analyze both multiphoton ionization of diatomic molecules and laser-assisted electron diatomic molecule scattering. The laser field is assumed to be monochromatic, monomode, spacially homogeneous and linearly polarized, where the molecular axis can be oriented in an arbitrary direction relative to the polarization direction. Multi-centre electron-molecule scattering programs have been modified in a straightforward way to obtain the solution in the internal region and single-centre atomic multiphoton propagator programs have been extended to solve the problem in the external region. The theory is illustrated by obtaining multiphoton ionization rates for a model Ha problem which enables the theory and computer programs to be tested by comparing the results against a completely independent atomic R-matrix Floquet program. The program is then used to obtain one- and two-photon ionization rates for Ha using an accurate wave function for Ha.