Rotational energy transfer in HF(v=2): Double resonance measurements and fitting law analysis

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Abstract
Data from overtone vibration‐laser double resonance experiments show extremely rapid rotational relaxation in HF (v=2) for rotational states up to J=6 and serve to test energy based fitting laws for rotational energy transfer rate constants. The observed rotational states equilibrate in less than a gas kinetic collision with some individual rates being more than twice the hard sphere collision rate. Energy based fitting laws reproduce the observed evolution of the state populations to within 30% but fail systematically for higher (J=5 and 6) rotational levels. Fitting laws formulated for collisions between an atom and a molecule are virtually as successful as those for collisions between two molecules. The extracted rate constants show that multiple rotational quantum energy transfer is an important aspect of relaxation dynamics.