MOLECULAR ROTATION AND THE OBSERVATION OF DIPOLE-BOUND STATES OF ANIONS

Electron photodetachment spectra have been measured in an ICR spectrom eter for the enolate ions of acetone, cyclobutanone, cyclopentanone, c yclohexanone, cycloheptanone, methyl vinyl ketone, pinacolone, propion aldehyde, and 1,1,1 -trifluoroacetone enolates. Electron affinities ha ve been determined for acetone enolate radical 1.758 +/- 0.019, cyclob utanone enolate radical 1.801 +/- 0.008, cyclopentanone enolate radica l 1.598 +/- 0.007, cyclohexanone enolate radical 1.526 +/- 0.010, cycl oheptanone enolate radical 1.444 + 0.02/-0.002, tert butyl methyl keto ne (pinacolone) enolate radical 1.755 + 0.05/0.005, propionaldehyde en olate radical 1.621 +/- 0.006, and 1,1,1-trifluoroacetone enolate radi cal 2.625 +/- 0.010 eV. Autodetaching dipole-bound states are observed in some but not all of these spectra. The mechanism for autodetachmen t of these states is discussed and it is seen that the binding of an e lectron by a dipole is very sensitive to the motions of the dipole. Th e motions of the dipole can be predicted from the rotational motions o f the molecule, allowing us to correlate the observation of dipole-bou nd states with the rotational motions of the dipole moment.