• B N Roy

      Articles written in Pramana – Journal of Physics

    • Alpha particle and deuteron impactL-shell ionization of Ar, Cu, Ge, Br, Zr and Ag

      S N Chatterjee B N Roy

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      Alpha particle and deuteron impactL-subshell ionization cross-sections of Ar, Cu, Ge, Br, Zr and Ag have been computed using Vriens’ expressions for ionization cross-section of atoms due to impact of heavy charged particles. The effects of Coulomb deflection of the projectile and increase in binding of the target electron in the presence of projectile have been incorporated. Hartree-Fock velocity distributions for the target electrons have been used in the present calculations. The simple binary encounter approximation model is found to give results which are in satisfactory agreement with those obtained from experiments and from other theories.

    • The effect of the relativistic Hartree-Fock-Roothaan momentum distribution in the binary encounter approximation for inner shell ionization

      V Kumar S N Chatterjee B N Roy

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      K- and L-shell ionization cross sections of gold due to impact of proton and alpha particles have been calculated in the binary encounter approximation incorporating the effects of Coulomb deflection of the projectile, of increase in binding of the target electron, and of polarization and relativity. Relativistic Hartree-Fock-Roothaan (RHFR) momentum distributions for the target electron along with an approximate relativistic correction to the collision dynamics have been used in the present calculations. A comparison with the corresponding calculations using non-relativistic Hartree-Fock-Roothaan wave functions, experimental results and other available calculations is presented.

    • Proton and α-particle impactM-shell ionization of atoms in binary encounter approximation

      Vijay Kumar S K Shrivastava B N Roy

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      M-shell ionization cross sections for atoms due to the impact of proton and α-particles have been calculated in the binary encounter approximation. The effects of Coulomb deflection of the incident projectile and increase in binding of the target electron have been investigated. Roothan-Hartree-Fock velocity distribution for the target electrons has been used in the present work. The calculated cross-sections have been compared with experimental results and other theoretical calculations wherever available. The present calculations give a good account of experimental observations.

    • Electron impact single and double ionization of halogens

      Gopaljee S N Chatterjee B N Roy

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      The binary encounter approximation has been used for calculations of electron impact single ionization cross-sections for F, Cl, Br and I and double ionization cross-sections for Br and I. Contributions of ionization from inner shells have also been included in the calculations. Hartree-Fock momentum distribution has been used for the bound electron as far as possible. The results have been found to be in satisfactory agreement with experimental observations.

    • Effect of distortion in electron impact excitation in Coulomb-projected Born approximation

      V Kumar B N Roy D K Rai

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      We have calculated total and differential cross-sections for 1sns (n = 2, 3, 4) electron impact excitation of hydrogen and hydrogenic ions at various energies in Coulomb-projected Born approximation. Distortion due to static interactions, target polarization and exchange effects has been incorporated in the initial channel. The present calculations have been compared with other theoretical and experimental results.

    • Electron impact ionization of Zn+ and Ga+

      Gopaljee S K Shrivastava B N Roy

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      We have investigated the contribution of excitation-autoionization to the electron impact ionization of Zn+ and Ga+ using the binary encounter approximation. Hartree-Fock velocity distributions for the bound electrons have been used throughout the calculations of direct and indirect ionization cross-sections. The calculated cross-sections are in good agreement with recent experiments. We have also compared our results with other theoretical calculations.

    • Electron impact double ionization of Ba and Ba+

      L K Jha S N Chatterjee B N Roy

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      Electron impact double ionization cross-sections for Ba and Ba+ have been calculated in the binary encounter approximation. Hartree-Fock velocity distribution has been used for the first ejected electron and a hydrogenic velocity distribution for the second. For Ba+ the focusing effects of the target ion on the incident electron have been incorporated in the calculations. Contributions from ionization-autoionization to the ionization cross-sections, as observed in experiments, have been included in the present work. The calculated results show structures as observed in recent experiments.

    • Electron impact ionization of Ba, Ba+ and Ba2+

      Gopaljee S K Shrivastava B N Roy

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      The binary encounter approximation has been used to investigate the effect of charge state of the target atom (ion) on the electron impact excitation autoionization cross-sections. Roothan-Hartree-Fock (RHF) velocity distribution for the bound electrons has been used through-out the calculations. The present results give a good account of the experimental observations.

    • Electron impact single ionization of copper

      L K Jha O P Roy B N Roy

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      Electron impact single ionization cross sections of copper have been calculated in the binary encounter approximation using accurate expression for σΔE as given by Vriens and Hartree-Fock momentum distribution for the target electron. The BEA calculation based on the usual procedure does not show satisfactory agreement with experiment in this case but a striking modification is found to be successful in explaining the experimental observations. The discrepancy is linked with the ionization of the 3d10 electrons and probably effective single ionization does not take place from 3d shell of copper leading to smaller values of experimental cross sections.

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