We have treated the Hulthén-modified separable potentials within the framework of the phase-function method and obtained a closed form expression fors-wave scattering phase shift. Specializing to a rank one separable potential we have found out the limiting conditions in which the Hulthén-modified phase shift goes over to its Coulomb counterpart. We demonstrate the usefulness of our approach by means of a model calculation.

We consider the scattering problem for absorptive interactions within the framework of phase-function method. A Green’s function approach is used to derive the phase equation. As a case study we apply the algorithm presented on a shallow α-α potential, the real and imaginary parts of which have been deduced from experimental data. The real and imaginary parts of theS-wave phase shift are found to vary smoothly with energy while those forD andG waves show some fluctuations in the low-energy region. It is shown that studies in spatial behaviour of the phase function provide a plausible explanation for the dynamical origin of these fluctuations.