Multiple ionization of xenon by positron impact

For positron impact on xenon we have measured the ratios of double-to-single and triple-to-single ionization cross sections, R2 and R3, respectively, and compared them with the corresponding cross section ratios for electron impact. At high projectile energies, at about 600-800 eV, the cross section ratios R2(e+) and R2(e-) merge. At lower projectile energies, the positron ratios lie below the electron ratios. Qualitatively, this agrees with the previous results for He, Ne and Ar. (author)