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.