M-RESOLVED COLLISION-INDUCED ROTATIONAL ENERGY / ALIGNMENT TRANSFER IN $CH_{4}$

Abstract

Experiments vary widely in their sensitivity to molecular space-fixed orientation. Fluorescence, absorption, raman, double resonance, and other techniques each have distinct dependencies on the M quantum number, and reactive collisions depend on relative orientations. The specific behavior of M on collision leaves its traces on the lineshapes and amplitudes in each type of experiment. Descriptive and rigorous angular momentum scaling tools like the statistical-tensor and tensor-opacity expansion provide a framework for understanding experimental observables and for modeling collisional interactions. It is quite common that state-to-state rates observed in 4-level DR experiments account for only about 70% of the linewidth seen in direct absorption. We relate this discrepancy to M-resolved collision-induced rotational energy/alignment transfer as part of the interpretation of results of 3 and 4 level DR experiments on ground-state E spin-modification Ievels in methane.