Quantum Calculation of the Sensitivity of Diffusion, Viscosity, and Scattering Experiments to the Intermolecular Potential

Abstract

Correlations between the form of the intermolecular potential as a function of distance and the quantum mechanical phase shifts as functions of the angular momentum quantum number have served as the basis for estimates of the sensitivity of viscosity, diffusion, and low‐energy scattering experiments to the attractive and repulsive portions of the intermolecular potential. The sensitivities of the experimental techniques are approximately as follows: repulsive portion of the potential, diffusion>viscosity>scattering; to the attractive region of the potential, scattering>viscosity=diffusion. Quantum diffusion and viscosity cross sections for the Lennard‐Jones potential have been calculated as functions of the reduced kinetic energy, K=μv²/2ε, and for decreasing values of the quantum parameter λ=h/σ(mε)^½. The cross sections for systems with λ corresponding to T₂, Ne, and CH₄ are equal to the classical cross sections for K>1.2. At lower K's the deviations from classical behavior become larger as λ increases.