Multiphoton rovibrational excitation of diatomic molecules in the presence of an intense infrared laser beam using a non-perturbative quasi-energy technique

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Abstract
A non-perturbative quasi-energy method has been developed to compute the rovibrational multiphoton excitation transition probabilities in diatomic (heteronuclear) molecules (in the electronic ground state) in the presence of an intense infrared laser beam. As the Floquet analysis is quite demanding computationally the authors therefore have resorted to a new non-perturbative quasi-energy method which not only reduces the computer time to a reasonable scale but also provides useful physical insights for the understanding of multiphoton absorption (MPA) dynamics. The practicability of this method is illustrated by computing the MPA spectra for OH, CO and HF molecules. The authors have compared their results with those obtained by exact Floquet and non-adiabatic Floquet analysis. A number of interesting features such as line broadening, dynamic Stark shift, hole-burning, etc., have been studied as a function of laser frequency and intensity.