Ultrahighhyphen;resolution photodetachment spectroscopy of acetaldehyde enolate negative ion has revealed sim;50 narrow resonances near threshold, corresponding to excitation to a diffuse state in which the electron is weakly bound by the field of the molecular dipole. A complete analysis of rotational transitions between the ground valence state and the excited dipolehyphen;bound state has been carried out, yielding spectroscopic constants and geometries for both states. In analogy to Rydberg states, the structure of the lsquo;lsquo;neutral corersquo;rsquo; of the dipolehyphen;bound state is like that of the neutral radical. The dependence of autodetachment lifetimes upon the rotational quantum numbers of the dipolehyphen;bound state has been measured. Bound levels of the dipolehyphen;bound anion state are readily electrichyphen;field detached. The selection rules and dynamics of autodetachment from the dipolehyphen;bound state are discussed.
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