Herbert P. Broida Award Winner: Lai-Sheng WangProbing Dipole-Bound States Using High-Resolution Resonant Photoelectron Imaging of Cryogenically-Cooled Anions

Negative ions do not possess Rydberg states, but polar anions may have diffuse dipole-bound states just below the detachment threshold, analogous to Rydberg states of neutral molecules. Excitation to vibrational levels of the dipole-bound state can induce autodetachment via vibronic coupling. The resulting resonant photoelectron spectrum is highly non-Franck-Condon and yields much richer vibrational information than conventional photoelectron spectroscopy. We developed an experimental apparatus integrating an electrospray ionization source with photoelectron spectroscopy, which allowed negative ions from solution samples to be studied in the gas phase. Subsequent development of a cryogenically-cooled Paul trap to create cold anions from electrospray has allowed high-resolution photoelectron imaging to be conducted for complex molecular anions, opening opportunities to probe dipole-bound excited states using photodetachment spectroscopy and resonant photoelectron imaging. I will present recent advances in our investigation of dipole-bound excited states, including the observation of p-type dipole-bound states and electron correlation induced by the electric field of the diffuse dipole-bound electron.