Unimolecular decomposition and vibrationally induced electron autodetachment of acetone enolate ion

Acetone enolate ion trapped in a pulsed ion cyclotron resonance spectrometer cell was irradiated with a pulsed CO2 laser. Both unimolecular decomposition to give HC2O− and CH4, and vibrationally induced electron autodetachment were observed. The data are consistent with a scheme in which a vibrationally excited enolate ion decomposes through an adiabatic (decomposition) pathway and a nonadiabatic (autodetachment) pathway. From an analysis of the branching using statistical reaction rate theory the autodetachment rate constant ka is estimated to be ∼107 s−1 at ∼1 eV above the electron detachment threshold.