Calculations of integral cross-sections for electron and positron impact of rare gas atoms

Abstract

In this paper, calculations of integral cross-sections for positron impact ionisation of rare gas atoms, at incident projectile energies from the ionisation threshold up to about 1 keV, by a distorted-wave method with close-coupled target states [D.L. Moores, Nucl. Instr. and Meth. B 143 (1998) 105] are extended to include He and to electron impact on all five targets. Results are compared with experimental measurements carried out at University College London with positrons and by E. Krishnakumar and S.K. Srivastava [J. Phys. B 21 (1988) 1055] and other authors with electrons. Cross-sections for ionisation of He by positron impact with simultaneous excitation of the He + ion are reported for the first time. Results of similar calculations for electron impact show discrepancies with previous experimental and theoretical work.