Probing the He-H₂ potential surface with dynamical and kinetic observables

This paper examines the effect of infinitesimal functional variations in a rigid rotor He-H₂ potential surface on several different levels of observables: inelastic cross sections, rate constants, and energy level populations. Equations are derived for the functional derivatives of these observables with respect to a variation in the potential surface. Sensitivities are presented with respect to the entire potential surface, as well as the individual Legendre components V_n(r). The dynamical and kinetic observables studied were found to be most sensitive to the V₂(r) term in the potential with the region of highest sensitivity dependent upon the energy or temperature as well as the states related by the individual observable. Sensitivity to the entire surface tends to show more structure due to interference among sensitivities to the individual components. While the main information on the underlying potential is retained, some information loss has been observed in the transition from the microscopic observables to the macroscopic ones.