CALCULATION OF THE PHOTODETACHMENT SPECTRUM FOR H3O-

The spectrum for the photodetachment of electrons from H3O- to produce H-2 + OH or H + H2O is calculated with the rotating bond approximatio n (RBA). This method treats explicitly three active degrees of freedom (two stretching vibrations and one bending mode) in both H3O- and the neutral reactive product. Potential-energy surfaces based on new ab i nitio calculations in these same three degrees of freedom are used. Co mparison with experimental photodetachment spectra demonstrates the ac curacy of the model and confirms that the experiment accesses photodet achment from both the H-(H2O) isomer of H3O-, producing H + H2O, and t he higher energy OH-(H-2) isomer yielding OH + H-2. In the latter case , a progression of bands associated with different OH rotational state s in the H-2 + OH product channel is predicted. The calculations sugge st that the observed photodetachment spectrum is mainly providing info rmation on the entrance and exit channels of the OH + H-2 --> H2O + H potential-energy surface quite close to the transition state.