Photodetachment spectroscopy and resonant photoelectron imaging of cryogenically-cooled deprotonated 2-hydroxypyrimidine anions

We report a photodetachment and high-resolution photoelectron imaging study of cold deprotonated 2-hydroxypyrimidine anions, C 4 H 3 N 2 O −. Photodetachment spectroscopy reveals an excited dipole-bound state (DBS) of C 4 H 3 N 2 O − with a binding energy of 598 ± 5 cm −1 below the detachment threshold of 26,010 ± 5 cm −1. Twenty vibrational levels of the DBS are observed as resonances in the photodetachment spectrum, with three below the detachment threshold and seventeen above the threshold. By tuning the detachment laser to the above-threshold vibrational resonances, highly non-Franck-Condon photoelectron spectra are obtained. Nine fundamental vibrational frequencies are resolved, including six symmetry-forbidden modes. The 598 cm −1 binding energy for the DBS is quite high due to the large dipole moment of the C4H3N2O radical (>6 D). However, no evidence of a second DBS is observed below the detachment threshold.