MICROWAVE STUDIES OF COLLISION-INDUCED TRANSITIONS BETWEEN ROTATIONAL LEVELS .6. CH3OH AND CH3NH2

The techniques of high-power microwave double and triple resonance have been applied to the study of collision-induced transitions between rotational levels of CH3OH and CH3NH2. Experiments have been carried out both for the pure gases and for mixtures with excesses of foreign gases, in particular He and H2. The results of the experiments and their quantitative analysis are summarized as follows: (i) Collisioninduced transitions in pure CH3OH were observed between rotational levels connected by μa and μb dipole selection rules ΔJ=0, ± 1, ΔK = 0, ±1. No collision-induced transitions were observed in pure CH3NH2. (ii) In CH 2OH-He, CH3OH-H-3, and CH3NH 2-He mixtures collision-induced transitions with ΔJ>1 have been observed strongly. This result was interpreted as showing that for collision-induced transitions in these mixtures the value of AJ is rather arbitrary while &K = Q is preferred, (iii) Collision-induced transitions between different torsional levels A↔E, A+↔-A-, and v= 1↔0 were searched but never found. This result shows that these transitions are orders of magnitude smaller than transitions in a single torsional level not only in pure sample but also in mixtures. For several four-level systems in pure CH3OH, observed results are compared with values derived from resistance network analogs to the four-level systems and dipolar rate constants calculated using Anderson's theory.