Sunanda Guha

Positronium formation in positron scattering from hydrogen and helium atoms: the distorted-wave approximation

The distorted-wave approximation is applied to investigate the rearrangement collision problem of positronium formation in the ground state with positron scattering from hydrogen and helium atoms for the positron energy ranges 8.704-200 eV and 20-100 eV respectively.

Model potential approach for positron-atom collisions. II. Positronium formation in excited ns states in Na, K, Rb and Cs using the first Born approximation

For pt.I see ibid., vol.13, no.9, p.1919 (1980). Cross sections are computed for positronium formation into an arbitrary excited s state during positron scattering from the alkali atoms using the first Born approximation. Considering both the post and the prior forms of the interaction potential in the calculation, the results are presented for the incident positron energies from 5 to 50 eV. From these results it is found that for the alkali atoms the Ps formation cross section satisfies the inverse n3 law consistently at all positron energies.

Electron capture by protons in collision with some alkali-like ions using a model potential approach

The process of H formation as a result of electron capture by protons from some alkali-like ions is investigated using the Coulomb-Born approximation with the full interaction potential. These ions are visualised as one-electron species to reduce the complexity of dealing with many-electron ions. In order to take the effect of the core electrons into account, the lone valence electron is assumed to move in the field of a model potential. Results for ground-state capture cross sections from Mg+, Ca+, Sr+ and Ba+ target ions are presented for several incident proton energies in the range 10-1000 keV retaining both the post and the prior forms of the interaction potential. The results for capture cross sections in the ground state in H++Mg+ ion collisions are compared with the available experimental findings.