Observation of dynamic Stark splitting in infrared-infrared double resonance in methyl fluoride☆

Abstract Dynamic Stark splitting has been observed by scanning the Q P (5, 3) transition in the 2 ν 3 - ν 3 band in 13 CH 3 F with a CO 2 -laser based infrared microwave sideband generator while pumping the Q R (4, 3) transition in the ν 3 band with a second CO 2 laser. Similar splitting has been observed in the Q Q (12, 9) and Q R (12, 9) transitions in the 2 ν 3 - ν 3 band of 12 CH 3 F while pumping the Q R (11, 9) transition in the ν 3 band. The lineshapes of these and other double resonance effects have been fit to high accuracy by means of a computer program that computes the spectrum by solving the density matrix equations for a three-level system including summation over the spatially degenerate states and numerical integration over the velocity. The effects of contributions from collisional energy transfer, frequency modulation of the lasers, and misalignment of the laser beams have been calculated and are discussed. Difficulties that must be overcome in order to use these experiments for determination of energy transfer rates are described.