COMPLEX SCATTERING LENGTHS IN MULTICHANNEL ATOM-MOLECULE COLLISIONS

It is shown that in the presence of inelastic scattering, zero energy elastic and inelastic scattering can be characterized by a complex sca ttering length, the imaginary part of which is related directly to the total inelastic scattering cross section. Collisions between H atoms and vibrationally excited H-2, molecules are investigated. Zero energy cross sections for all vibrational states of H-2 and the correspondin g complex scattering lengths are reported using accurate quantum mecha nical calculations. We obtain large values of the elastic cross sectio ns which we attribute to s-wave bound and quasi-bound states of H ... H-2(v). The energies and lifetimes of the quasi-bound states are extra cted from the complex scattering lengths. (C) 1997 Elsevier Science B. V.