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Abstract

We develop an analytic model of thermal state-to-state rotationally inelastic collisions of asymmetric-top molecules with closed-shell atoms in electric fields, and apply it to the Ar--H₂O collision system. The predicted cross sections as well as the steric asymmetry of the collisions show at fields up to 150 kV/cm characteristic field-dependent features which can be experimentally tested. Particularly suitable candidates for such tests are the 0₀₀ -> 2₂₀ and
1₁₀-> 2₂₁ channels, arising from the relaxation of the field-free selection rules due to the hybridization of J states. Averaging over the M' product channels is found to largely obliterate the orientation effects brought about by the field.