Interference phenomena in two-photon transitions caused by laser-induced ac-Stark effect

Abstract

A system is described in which a real molecular state is tuned into and out of resonance with the intermediate level of a two-photon transition, by the laser-induced ac-Stark effect. Two narrow-band CO2 wave-guide lasers are utilized to induce rovibrational transitions in the ν3 ladder of SF6. A weak probe laser monitors the absorption for the [Formula: see text] two-photon transition. Simultaneously, a strong pump laser is in resonance with the [Formula: see text] one-photon transition. The ac-Stark splitting is observed and quantum interferences between two-photon amplitudes involving different intermediate states occur. It is demonstrated that destructive interference allows suppression of the two-photon excitation for an appropriate pump laser power. Simulations based on the Dressed State Picture and the optical Bloch equations show a satisfactory agreement with the experiment.