INVESTIGATION OF COLLISION-INDUCED TRANSITIONS FOR CH3BR BY RADIOFREQUENCY INFRARED DOUBLE-RESONANCE

The highly sensitive method of radio-frequency-infrared double resonance spectroscopy inside the cavity of a CO2 laser has been applied to the study of collision-induced transitions of CH3 79Br and CH3 81Br in the four level scheme. Various types of radio-frequency transitions corresponding to A1-A2 and pure quadropole resonances were observed as a result of collision population transfer between different rotational levels. Thus, collision-induced dips have been measured in the pure gas and in mixtures with polar carbonyl sulfide (OCS) and nonpolar (He, Ar) foreign gases. Clamping experiments were also done, using a second radiation in a six level triple resonance configuration to investigate collision selection rules. The intensity ratios of the collision-induced dips to the corresponding three level double resonance signals were measured for a number of transitions in the ground and in excited vibrational states. Collision selection rules in the pure gas and in mixtures with polar and nonpolar foreign gases are discussed. © 1990 American Institute of Physics.