The Glauber amplitudes for the general transitionnlm→n’l’m’ in charged particle hydrogen atom collisions have been obtained in the form of a one-dimensional integral. The final expression involves only a few hypergeometric functions ifn is not too large and is particularly suited to study excitation to highly excited states from a low lying state.

The Coulomb-Glauber approximation is applied to evaluate the electron-impact excitation integrated cross sections for 1¹S —n¹P (n=2, 3) transitions in helium-like ions, C⁴⁺, N⁵⁺, O⁶⁺ and Ne⁸⁺. The results are presented in terms of scaled collision strengthn³Z²k_i²σ and scaled integrated cross-sectionZ⁴σ. Our values when compared with other available theoretical results are found to be larger than the Coulomb-Born and distorted wave polarised orbital (DWPO) values.

Total charge transfer cross-sections for protons impinging on hydrogen has been calculated in Coulomb-projected Börn approximation. It is seen that the present calculation compares well with the available experimental data.

The triple differential cross-sections for the ionization of atomic hydrogen by fast electrons are considered in the case of a coplanar symmetric energy-sharing geometry. They are estimated in the modified Glauber (MG) approximation. It is found that MG results are significantly different from those in the second Born approximation only for 90°⩽ϑ⩽110°. Outside this range they are almost identical.

Triple differential cross-sections for the ionization of helium by fast positrons are calculated in a ‘correlated’ first Born approximation supplemented by the inclusion of post-collision interaction effects. The results are analysed with respect to electron-helium experimental data of Jung and coworkers in coplanar asymmetric geometry.

The elastic differential cross-section forē-Na scattering in the presence of non-resonant laser field is studied for the exchange ofℓ=0, 1, 2 photons. The undressed contribution is evaluated within the framework of the eikonal Born series approximation and the effect of exchange is taken into account via the Ochkur approximation. The sodium atom has been treated in the frozen core approximation with special attention to the effect of the dressing of the target by the laser field. The ‘dressing’ of the target leads to quite an increase in the cross-section over the ‘undressed’ value near the forward direction for the exchange of one or two photons.

Triple differential cross-sections for the electron and positron impact ionization of atomic hydrogen and helium are calculated in a first order model using a product of two Coulomb wavefunctions for the final state continuum electrons supplemented by post-collision interaction effects.

Triple differential cross-section for electron and positron impact ionization of hydrogen and helium are calculated by using the Glauber approximation along with post-collision interaction effects which are estimated classically. The present results are compared with the recent absolute data of Ehrhardt, Jung and coworkers for the electron impact case. The positron impact case is found to lead to a larger binary to recoil peak maxima ratio (compared to the electron impact case) which further increases when post-collision interaction effects are included.

The triple differential cross-sections for the ionization of hydrogen by electron impact in the presence of a laser field have been calculated in the coplanar asymmetric geometry by using the first Born approximation and the symmetric geometry by using the Coulomb-Born approximation at an incident electron energy of 250 eV. The variation of the triple differential cross-sections, for fixed values of the angles of scattering and ejection, is studied as a function of the linear polarization of the laser field. The changes are quite amenable to experimental investigation.

Simultaneous ionization and excitation of helium by electron impact is considered in an improved second Born approximation. The wave function of the low energy ejected electron is obtained in the field of residual He⁺ ion in 2s-state. The calculation has been done for the processe⁻+He→e⁻+He⁺(2s)+e⁻ in the coplanar asymmetric geometry with Hartree-Fock wave function of Byron and Joachain for the helium ground state and the results are compared with the absolute experimental data of Dupreet al [J. Phys.B25, 259 (1992)] at ∼ 5.5 keV incident energy. Our results are found to increase the ratio of the recoil peak to binary peak intensity by about 30% over the first Born results and thus to bring it closer to the experimental data.