Global Franck-Condon Breakdown Resulting from Cooper Minima

Abstract

Using N 2 2σ u − 1 photoionization as an example, we present the first measurements and calculations of photoion vibrational distributions for an extended energy range (5 ≤ E k ≥ 230 eV).The results show a striking breakdown of the Franck-Condon approximation over a 100 eV range.We show that this coupling between vibrational and electronic motion arises from a dependence of Cooper minima on molecular bond length.Based on this mechanism, the effect is expected to be common for molecular systems. © 1996 The American Physical Society.