ASYMPT: a program for calculating asymptotics of hyperspherical potential curves and adiabatic potentials

A FORTRAN program is presented which calculates asymptotics of potential cu rves and adiabatic potentials with an accuracy of O(rho(-2)) in the framewo rk of the hyperspherical adiabatic (HSA) approach. Here, rho is the hyperra dius. It is shown that matrix elements of the equivalent operator correspon ding to the perturbation rho(-2) have a simple form in the basis of the Cou lomb parabolic functions in the body-fixed frame and can be easily computed for high values of total orbital momentum and threshold number. The second -order corrections to the adiabatic curves are obtained as the eigenvalues of the corresponding secular equation. The eigenvectors computed are used t o calculate the relevant corrections to matrix elements of potential coupli ng. The asymptotic potentials obtained can be used for the calculation of t he energy levels and radial wave functions of two-electron systems in the a diabatic and coupled-channel approximations of the HSA approach and also in scattering calculations. (C) 2000 Elsevier Science B.V. All rights reserve d.