Characterization of photoionization intermediates via ab initio molecular dynamics

Ab initio molecular dynamics (AIMD) allows one to probe complex potential e nergy surfaces at finite temperatures. Here we extend this technique to the analysis of vertical excited states along ground-state AIMD trajectories. We illustrate this idea via comparison to the silver trimer anion photoioni zation experiments of Boo et al. (J. Phys. Chem. 1997, 101, 6688). This wor k displayed an aberrant trend in the ionization efficiency near threshold, which suggests the presence of an intermediate state resonance. We present an AIMD simulation at the complete active space self-consistent field lever of the silver trimer anion photoionization to groundstate neutral silver t rimer for several different basis set expansions. We have analyzed the exci ted-state manifold via multireference singles and doubles configuration int eraction (MRSDCI) and complete active space second-order perturbation theor y (CASPT2) calculations performed at representative paints along the neutra l silver trimer trajectories in order to discern the nature and relative en ergy of the intermediate excited-state probed in the experiment. We find an excited state that may coincide with the possible resonance state accessed by the similar to 400 nm probe and a higher near-linear excited state that may have been accessed by the similar to 270 nm probe in the photoionizati on experiments.