• K N Joshipura

      Articles written in Pramana – Journal of Physics

    • Differential and integral cross-sections of e-O2, O3, NO, CO scattering at energies 100–1000 eV

      P M Patel K N Joshipura

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      A modified additivity rule is formulated to calculate the differential cross-sections for elastic scattering of electrons from molecules. It improves the results at small angles and at relatively lower incident energies (<1000 eV). Integral cross-sections calculated presently are combined with the known total ionization cross-sections to obtain total (complete) cross-sections. An extension of the present approximation to larger molecules is also suggested.

    • Ionization and excitation of some atomic targets and metal oxides by electron impact

      K N Joshipura B G Vaishnav C G Limbachiya

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      We have calculated total inelastic and total ionization cross-sections for collisions of electrons on atomic targets oxygen (O), aluminium (Al) and copper (Cu) and metal oxides AlO and Al2O, at impact energies from near excitation threshold to 2000 eV. A complex (optical) energy-dependent interaction potential is used to derive total inelastic cross-sections resulting from ionization as well as excitation processes. The inelastic cross-sections are bifurcated into discrete and continuum contributions and total ionization cross-sections have been deduced therefrom. Our calculation also provides information, hitherto sparse, on the excitation processes in the atomic targets O, Al, Cu and metal oxides AlO, Al2O. Adequate comparisons are made with other theoretical and experimental data.

    • Total and ionization cross-sections of N2 and CO by positron impact: Theoretical investigations

      Harshit N Kothari K N Joshipura

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      In this paper we report our calculations on several important total cross-sections (TCS$_s$) of positron impact on isoelectronic N2 and CO molecules, treated in the complex spherical potential formalism. Basically the total (complete) cross-section $Q_T$ consists of elastic and inelastic contributions. Our total inelastic cross-section ($Q_{\text{inel}}$) contains ionization and electronic excitations together with positronium formation. Our goal here is to bifurcate $Q_{\text{inel}}$ further to deduce total ionization cross-section, using the `complex scattering potential–ionization contribution’ (CSP-ic) method of electron–atom/molecule scattering. The present range of positron energy is 15–2000 eV. All the resulting cross-sections are in a good general accord with the existing data. This work highlights the importance of various scattering channels in $e^+ - N_2$ and $e^+ - CO$ interactions at intermediate and high energies.

    • Total (complete) and ionization cross-sections of argon and krypton by positron impact from 15 to 2000 eV – Theoretical investigations

      Harshit N Kothari K N Joshipura

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      Considering interactions and scattering of positrons with argon (Ar) and krypton (Kr) atoms, we have calculated total cross-sections $(Q_{T} = Q_{el} + Q_{inel})$ using complex spherical potentials for these systems. In positron–atom scattering it is difficult to bifurcate the ionization and cumulative excitation contained in the total inelastic cross-section. An approximate method called CSP-ic (complex scattering potential-ionization contribution) similar to electron–atom scattering has been applied to bifurcate ionization and cumulative excitation cross-sections at energies from the threshold to 2000 eV. Adequate comparisons of the present results are made, with available data.

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