Positron-impact ionization of highly charged ions in lowest-order QED theory

Abstract

Lowest-order QED theory using distorted-wave states is applied to the calculation of positron-impact ionization cross sections for highly charged atomic ions. Electron and positron ionization cross sections for atomic ions are predicted to differ by substantial amounts in the threshold region. For highly charged ions like U +, the smaller positron ionization cross section is more strongly affected by transverse photon interactions than the corresponding electron ionization cross section. At twice the threshold for U + ionization, the annihilation terms are found to reduce the positron cross section by about 12%.PACS number(s): 34.80.Kw

Relativistic electron- and positron-impact ionization of U91 , U90 , Pu93 and Pu92

“…In figure 5, our results for the reduced total cross section of electron-impact ionization for U 91+ are compared with experimental data of Claytor et al (1988) and Marrs et al (1994), as well as with theoretical results of Pindzola et al (1989) and Fontes et al (1999) theoretical results of Pindzola et al (1989) and Pindzola (1992). In figure 7, our reduced total cross section of positron-impact ionization for U 90+ is compared with that of Pindzola (1992).…”

“…In figure 5, our results for the reduced total cross section of electron-impact ionization for U 91+ are compared with experimental data of Claytor et al (1988) and Marrs et al (1994), as well as with theoretical results of Pindzola et al (1989) and Fontes et al (1999) theoretical results of Pindzola et al (1989) and Pindzola (1992). In figure 7, our reduced total cross section of positron-impact ionization for U 90+ is compared with that of Pindzola (1992). The QED effects, which are not accounted for in the present approach, seem to improve the agreement with the experimental data of Marrs et al The experiment of Claytor et al, on the other hand, seems to greatly overestimate the measured cross section.…”

“…Electron-impact ionization cross sections were calculated by Pindzola et al (1989) for U 91+ and U 90+ , using a triple partial-wave expansion in the lowest-order QED theory and by Moores and Pindzola (1990) for hydrogenic ions with nuclear charge Z between 26 and 92 in a relativistic distorted-wave method. Pindzola (1992) also calculated positron-impact ionization cross sections for highly charged ions. Fontes et al (1999) studied 1s ionization cross sections within the relativistic distorted-wave approximation, including the generalized Breit interaction, for a variety of ions, with one to four bound electrons and nuclear charge Z in the range of 10 Z 92.…”