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

In this paper, calculations of integral cross-sections for positron impact ionisation of rare gas atoms, at incident projectile energies from the ioni sation threshold up to about 1 keV, by a distorted-wave method with close-c oupled 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. Res ults 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 f or electron impact show discrepancies with previous experimental and theore tical work. (C) 2001 Elsevier Science B.V. All rights reserved.