Laserndash;laser infrared double resonance has been used to study energy transfer from the12CH3F to the13CH3F isotopic species. The12CH3F ngr;3mode was pumped by aQhyphen;switched 9.6 mgr; CO2laser operating on theP(20) line, while the13CH3F ngr;3absorption was monitored by a cw CO2laser operating on theP(32) 9.6 mgr; transition. Equilibration of the ngr;3modes in the two isotopes occurs in approximately six gas kinetic collisions. Evidence for a somewhat slower equilibration of the ngr;6modes in the two isotopes has also been observed. These results give further support to the idea that ladder climbing collisions can lead to a rapid redistribution of energy into high lying states of polyatomic molecules.
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