QUANTUM-MECHANICAL CALCULATION OF INELASTIC-SCATTERING OF AN ATOM BY A LARGE ANHARMONIC CLUSTER - APPLICATION TO HE-13(AR)

An approximate quantum mechanical method is proposed for the calculati on of inelastic scattering of an atom from a large anharmonic cluster or molecule. The method is based on: (a) computing the vibrational sta tes of the cluster (or molecule) in the vibrational self-consistent fi eld approximation; (b) treating the scattering of the atom to a first approximation as taking place from a vibrationally frozen cluster; (c) obtaining inelastic transitions by a distorted wave approximation, wh ere the coupling is the vibrationally dependent part of the atom/clust er potential. Computationally convenient expressions are worked out. T he method is applied to He scattering from Ar-13 and the results are c ompared to experimental data for size-dispersed clusters. Good qualita tive agreement is found. The merits of the proposed method compared wi th alternative approaches are discussed. (C) 1998 American Institute o f Physics. [S0021-9606(98)00215-3].