Slow Photoelectron Velocity-Map Imaging Spectroscopy of the ortho-Hydroxyphenoxide Anion

We report high-resolution photodetachment spectra of cryogenically cooled ortho-hydroxyphenoxide anions (o-HOC6H4O-) using slow photoelectron velocity-map imaging spectroscopy (cryo-SEVI). We observe transitions to the three lowest-lying electronic states of the ortho-hydroxyphenoxy radical, and resolve detailed vibrational features. Comparison to Franck-Condon simulations allows for clear assignment of vibronic structure. We find an electron affinity of 2.3292(4) eV for the neutral (X) over tilde (2)A '' ground state, improving upon the accuracy of previous experiments. We measure term energies of 1.4574(7) eV and 1.5922(48) eV for the (A) over tilde (2)A' and (B) over tilde (2)A '' excited states respectively, representing their first resolution and clear assignment. Photodetachment threshold effects are considered to explain the structure of these bands.