Communication: Observation of dipole-bound state and high-resolution photoelectron imaging of cold acetate anions.

We report the observation of a dipole-bound state and a high-resolution photoelectron imaging study of cryogenically cooled acetate anions (CH3COO(-)). Both high-resolution non-resonant and resonant photoelectron spectra via the dipole-bound state of CH3COO(-) are obtained. The binding energy of the dipole-bound state relative to the detachment threshold is determined to be 53 ± 8 cm(-1). The electron affinity of the CH3COO· neutral radical is measured accurately as 26 236 ± 8 cm(-1) (3.2528 ± 0.0010 eV) using high-resolution photoelectron imaging. This accurate electron affinity is validated by observation of autodetachment from two vibrational levels of the dipole-bound state of CH3COO(-). Excitation spectra to the dipole-bound states yield rotational profiles, allowing the rotational temperature of the trapped CH3COO(-) anions to be evaluated.