Shyamal Datta

Evaluation of Coulomb integrals with hydrogenic and Slater-type orbitals

A method has been developed for the evaluation of Coulomb integrals containing the product of the Coulomb wavefunction (r/K) with either the hydrogenic or Slater-type orbital (r/nlm) in closed form in terms of the Gauss hypergeometric function for an arbitrary nlm state. The results are of direct use for charge transfer in the impulse, the continuum distorted-wave and the continuum intermediate state approximations.

Differential cross sections for excitation of the helium atom by proton impact

The differential cross sections for the excitation of helium atoms to the n=2 level are calculated in the high-energy region by applying the Coulomb-projected Born approximation as proposed by Geltman (1971). Good agreement in the angular distribution is obtained with recently published data.

Electron capture by fast protons from carbon, neon and argon in the Coulomb Born approximation

The Coulomb Born approximation formulated by imposing the asymptotically exact boundary conditions on the scattering wavefunctions and the perturbation potentials is used to compute total cross sections for electron capture by fast protons from carbon, neon and argon atoms at intermediate and high energies. An independent particle model is employed with a one-electron orbital for the multielectron target atom. Three sets of numerical computations are presented in which the initial state of the active electron is described by either a Roothan-Hartree-Fock wavefunction or a hydrogenic wavefunction with standard or experimentally derived effective charges. The present calculated results are found to be in good agreement with existing experimental data in the intermediate and high energy region.

Charge transfer in He2+-H(1s) collisions

Charge-transfer cross sections from the ground state of atomic hydrogen into the final 1s, 2s and 2p states of the He+ ion, by alpha particles are calculated in the Coulomb-Born approximation. The results are compared with the existing experimental findings and other theoretical calculations. Throughout the energy region of the incident projectile, the present calculated results are found to show a trend similar to other results obtained by applying many-state close-coupling calculations. The present two-state calculated results are in satisfactory agreement with the existing many-state calculated results as well as with the available experimental findings.