Articles written in Pramana – Journal of Physics
Volume 63 Issue 5 November 2004 pp 1063-1072
Three different types of ionization and excitation processes are studied in detail for the scattering of positronium (Ps) by the simplest alkali atom (Li) using a Coulomb-Born approximation for ionization and first-Born approximation for excitation. This is the first work where orthogonalized Coulomb wave is used to represent the ionized electron for Ps-Li scattering using a single-electron and a three-electron prescription of the target. Li is chosen to minimize the effect of intrinsic correlation among the target atomic electrons so that it can extract the basic physics more accurately. All the possible Coulomb interactions are considered exactly. Comparative studies of different cross-sections using two different representations of the target provide us the informations to enrich our ideas about the system and the important role of core electrons.
Volume 66 Issue 2 February 2006 pp 415-422
To improve the Coulomb-Born approximation (CBA) theory of ionization in positronium (Ps) and atom scattering, the effect of exchange is introduced. The nine-dimensional exchange amplitude for ionization of Ps in Ps—H scattering is reduced to a two-dimensional integral using the present Coulomb-Born-Oppenheimer approximation (CBOA). The methodology is extremely useful to evaluate ionization parameters for different target systems and for different types of ionization processes. It is then applied to evaluate the Ps-ionization cross-section and to estimate the effect of exchange on Psionization in Ps-H system. We establish the importance of exchange at lower energy region.
Volume 83 Issue 6 December 2014 pp 907-914 Research Articles
A modified static-exchange model is developed to study the collision of an atom with another atom. It includes the effect of long-range dipole–dipole van der Waals interaction between two atoms in addition to the exact effect of short-range force due to Coulomb exchange between two system electrons. Both these interactions dominate at colder energies. The system is treated as a four-centre problem in the centre-of-mass frame. The present
Volume 94, 2019
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