Quantum-state-resolved scattering of lithium hydride

A technique for the determination of integral rotationally inelastic state-resolved cross sections, which involves electric quadrupole state selection of a molecular beam and tunable laser fluorescence detection of the final states, is reviewed. This method has been applied to the scattering of lithium hydride, and results with a number of targets (helium and several polar molecules) are presented. The experimental results are compared with calculations by M.H. Alexander and D.M. Silver which employed a number of theoretical treatments of varying sophistication. One clear result of this collaborative effort is the conclusion that rotational energy transfer, both for LiH-He and for polar molecule collisions, cannot be described adequately by simple models but requires detailed consideration of the interplay between translational and rotational motion, as well as a realistic description of the intermolecular forces