			15min:

SIMULATING THE PHOTOELECTRON SPECTRA OF HYDRATED-ELECTRON CLUSTERS USING AB INITIO\/ MOLECULAR DYNAMICS.

JOHN M. HERBERT, Department of Chemistry, The Ohio State University, Columbus, OH 43210.

Ab~initio\/ molecular dynamics methods are used to simulate photoelectron spectra of small water cluster anions, (H₂O)_n^-, including the effects of thermal fluctuations in the geometry of the cluster. Even at temperatures well below 300~K, such fluctuations can significantly alter the vertical electron binding energy (VEBE), and the maximum in the photoelectron intensity distribution typically does not coincide with the VEBE calculated at the minimum-energy geometry. This thermal shift in VEBE can be comparable to, or even large than, the effects of high-level treatments of electron correlation. Simulated photoelectron spectra of (H₂O)₄^- are in quantitative agreement with experiment for molecular dynamics simulations in the range of 150--200~K, and indicate that the experiments probably do not sample a thermodynamic distribution of cluster anions.