Autoionization process in the Penning ionization of the CO molecule by Ne* (P-3(0), P-3(2)) metastable atoms

Penning ionization electron spectroscopy of the CO molecule by Ne* (P-3(2), P-3(0)) metastable atoms is reported. An extensive vibrational excitation of the electronic ground state X(2) Sigma(+) of the CO+ ion is observed. The measured angular distribution of the electrons corresponding to the first vibrational states (upsilon = 0-1) is anisotropic, while that of the higher levels is isotropic. A quasi-resonant excitation transfer process, leading to excitation of the molecular target into an intermediate autoionizing Rydberg state, is proposed to explain the discrepancy between the Franck-Condon factors and the observed excited vibrational levels of the X(2) Sigma(+) state.