OBSERVATION OF TRANSFERRED SPIKES IN${1-3}CH_{3}F$ BY INFRARED-INFRARED FOUR-LEVEL DOUBLE $RESONANCE^{1}$

Abstract

Infrared-infrared four-level double resonance has been observed by pumping the R(4,3) transition in the $\nu_{3}$ fundamental band of $^{13}CH_{3}F$ by means of a $CO_{2}$ laser and by probing vibration-rotation transitions in the $2\nu_{3}-\nu_{3}$ hot band with an infrared microwave sideband laser spectrometer. Sharp transferred spikes in the velocity distribution were observed in transitions originating from (J,3) levels $(\Delta K = 0)$, but not from other levels. The transferred spikes were observed for J values up to 22, corresponding to $\Delta J = 17$. The spikes are sharp up to about $\Delta J = 5$ and are rather broad for $\Delta J > 10$. If the principal selection rule for collisionally-induced transitions is $\Delta J = 0$ or $\pm 1$, the observation of spikes for $J = 22$ indicates that there is still some conservation of velocity after as many as 17 collisions. A value for the mean change in velocity upon collision will be reported and its variation with J will be discussed.