Breakdown of the born-oppenheimer approximation in ZEKE states of Ag2

Recently we reported on vibrationally resolved spectra of the ionic ground state of Ag 2 + via ZEKE spectroscopy. The vibronic intensity distributions could not be interpreted within the Franck-Condon scheme. Here, we show that it is possible to overcome this discrepancy by invoking the breakdown of the Born-Oppenheimer approximation in the ZEKE states of silver dimer. A comparison of the spectral structure of the direct ion signal with simultaneously recorded ZEKE band profiles further illustrates this non-Franck-Condon behavior.