We use a nonperturbative treatment to study multiphoton transitions in molecules with permanent dipole moments. This generalizes the perturbative treatment of Scharf and Band (Chem. Phys. Letters 144 (1988) 165) for two-photon transitions in molecules with permanent dipole moments in the presence of electromagnetic fields of two frequencies, one near resonance and the other small, Our nonperturbative density matrix treatment accounts for level population decay (T1) effects and optical transition dephasing (T2) effects, both neglected in earlier approaches. Our results are applicable even in the regime where perturbation theory breaks down. In particular, when the sum of the field frequencies approaches a molecular resonance a substantial enhancement of the photo-absorption rate (by a two-photon process) occurs even when one frequency becomes as small as the transition linewidth.
ASJC Scopus subject areas
- Physics and Astronomy (all)
- Physical and Theoretical Chemistry