Molecular rotation and the observation of dipole‐bound states of anions

Electron photodetachment spectra have been measured in an ICR spectrometer for the enolate ions of acetone, cyclobutanone, cyclopentanone, cyclohexanone, cycloheptanone, methyl vinyl ketone, pinacolone, propionaldehyde, and 1,1,1‐trifluoroacetone enolates. Electron affinities have been determined for acetone enolate radical 1.758±0.019, cyclobutanone enolate radical 1.801±0.008, cyclopentanone enolate radical 1.598±0.007, cyclohexanone enolate radical 1.526±0.010, cycloheptanone enolate radical 1.444+0.02/−0.002, tert‐butyl methyl ketone (pinacolone) enolate radical 1.755+0.05/0.005, propionaldehyde enolate radical 1.621±0.006, and 1,1,1‐trifluoroacetone enolate radical 2.625±0.010 eV. Autodetaching dipole‐bound states are observed in some but not all of these spectra. The mechanism for autodetachment of these states is discussed and it is seen that the binding of an electron by a dipole is very sensitive to the motions of the dipole. The motions of the dipole can be predicted from the rotational motions of the molecule, allowing us to correlate the observation of dipole‐bound states with the rotational motions of the dipole moment.