Multidimensional Franck-Condon simulations of photodetachment spectra for the formate-water cluster anion: investigating H atom transfer along the HCOOH+OH reaction coordinate.
A new multidimensional Franck-Condon (FC) simulation methodology was applied to an anionic-neutral cluster transition for the first time to investigate the use of photodetachment spectroscopy of the HCOO(-).H(2)O anion as a means to study the HCOO.H(2)O and HCOOH.OH neutral clusters. For the HCOO(-).H(2)O to HCOO.H(2)O transition, vibrationally resolved simulated spectra were obtained across the threshold detachment region, indicating that photodetachment spectroscopy of the respective anionic cluster should provide detailed structural information on the bifurcated HCOO.H(2)O neutral cluster. The simulations predict that the photodetachment spectra should display prominent progressions of both the intermolecular stretch and the in-plane OCO bending mode. In contrast, for the HCOO(-).H(2)O to HCOOH.OH transition, the vibronic FC simulations resulted in transitions with negligible intensities, despite the fact that the geometries of the respective anionic and neutral systems were similar. The low FC intensities were traced to the large off-diagonal elements of the Duschinsky matrix for this transition, which arise due to the considerable differences in the vibrational wave functions following hydrogen transfer.