An analytic algebraic approach to study the influence of molecular alignment and orientation on multiphoton excitation in intense laser fields

The influence of molecular alignment and orientation on multiphoton vibrational excitation of diatomic molecules H-2, HD, and D-2 is studied by an analytical algebraic approach. The explicit expressions of the time-evolution operator and the excitation probability are given. The long-time average absorbed energy spectra and the time-dependent absorbed energy are obtained. Results show that the impact of molecular orientation on the multiphoton resonant excitation is decided by the molecular type and molecular anharmonicity. This is valuable for controlling the vibrational excitation of molecules, which is relevant to the whole field of molecular physics and physical chemistry. Furthermore, good agreement with numerical simulation is achieved.