INTERFERENCE PHENOMENA IN 2-PHOTON TRANSITIONS CAUSED BY LASER-INDUCED AC-STARK EFFECT

A system is described in which a real molecular state is tuned into an d out of resonance with the intermediate level of a two-photon transit ion, by the laser-induced ac-Stark effect. Two narrow-band CO, wave-gu ide lasers are utilized to induce rovibrational transitions in the v(3 ) ladder of SF6. A weak probe laser monitors the absorption for the la ] --> Ic] two-photon transition. Simultaneously, a strong pump laser i s in resonance with the la] --> Ib] one-photon transition. The ac-Star k splitting is observed and quantum interferences between two-photon a mplitudes involving different intermediate states occur. It is demonst rated that destructive interference allows suppression of the two-phot on excitation for an appropriate pump laser power. Simulations based o n the Dressed State Picture and the optical Bloch equations show a sat isfactory agreement with the experiment.