MODE DEPENDENCE IN VIBRATIONAL-EXCITATION OF A CO2 MOLECULE BY ELECTRON AND POSITRON IMPACTS

We have found theoretically, for the first time, that vibrational exci tations of a CO2 molecule by electron (e(-)) and positron (e(+)) impac ts are strongly dependent on the charge of the projectile at impact en ergy below 6 eV. For the symmetric-stretching mode, the excitation cro ss section of e(-) impact is larger by 2 to 3 orders of magnitude than that of e(+) impact, while for bending and asymmetric-stretching mode s the magnitude of both cross sections for e(-) and e(+) impacts is ne arly comparable. These results are qualitatively confirmed experimenta lly, and are interpreted as the difference of interactions and inciden t e(-) or e(+) wave functions.