Vibrational state distributions resulting from associative ionization in Na(3p)-Na(3p) collisions

We report on the vibrational energy distribution in Na-2(+)(X(2) Sigma(g)(+)) ions resulting from the associative ionization reaction between two Na(3p) atoms as determined via their wavelength-dependent photodissociation. Results at 10, 25, 85 and 140 meV mean collision energy were obtained for excitation of the sodium atoms with circularly polarized light. For 10 and 25 meV mean collision energy the results show a dominant population of the v = 3 state (55% and 33%, respectively). For 85 meV collision energy two maxima are found, located near v = 3 and 7, whereas for 140 meV the results show a roughly linear increase of the vibrational population with v within the wavelength range measured. These results are in agreement with previously published results for conditions where a comparison was possible. Measurements at 25 meV exciting with linearly polarized instead of circularly polarized light do not differ significantly from the results mentioned above. The measured vibrational state distributions give information on the shape, at small internuclear distances, of the diabatic molecular potential curve(s) involved in the associative ionization process.