Abstract

We present the results of measurement of collisional and collisionless IR absorption spectra in the quasi-continuum (QC) of two polyatomic molecules—C₂F₅CI and SF₆. A two-frequency pump -probe arrangement was used in all the experiments. The basic scheme involved the use of a 80-ns multilongitudinal mode pulse from a TEA CO₂ laser to preheat the molecules to a desired level in the quasi-continuum followed by a weak picosecond or nanosecond probe pulse. The ultrashort picosecond IR pulses were generated by the process of optical free induction decay. The probe pulse was delayed with respect to the pump pulse by an appropriate electronic delay commensurate with gas pressure to endure V-V and V-R but not V-T relaxation prior to probing the QC.

© 1986 Optical Society of America