ULTRASHORT-LIVED NON-RYDBERG DOUBLY-EXCITED RESONANCES OBSERVED IN MOLECULAR PHOTOIONIZATION

The N-2(+)(B - X) dispersed fluorescence from photon excited N-2 molec ules has been measured in the 19-34 eV excitation range, where our the ory predicts the existence of non-Rydberg doubly excited resonances wh ich autoionize in the sub-fs regime into the N-2(+) B-2 Sigma(u)(+) io nic state. The experimentally deduced vibrational branching ratios (v' = 1)/(v' = 0) revealed five prominent features, four of which could b e identified as such doubly excited resonances based on the lowest ord er of the many-body perturbation theory.