Electron spectrometric study of the internal energy distribution in Na2+ for single beam associative ionization

We present the internal energy distribution of Na2+ molecular ions formed in the associative ionization (AI) reactions Na(3p)+Na(3p)→Na2++e- and Na(4d)+Na(3s)→Na2++e-, as measured in a single beam by electron spectrometry. In both reactions the population of the higher vibrational levels is favoured. The cross section of the second reaction is found to be about two orders of magnitude larger than that of the first. The internal energy distribution of Na2+ due to the first reaction is independent of the polarization of the colliding laser excited atoms. This is in agreement with theoretical findings that only one molecular potential curve leads to AI in the first process. Also the distribution itself, with maximum population for the vibrational levels v = 2 and v = 3, agrees well with theory.