Femtosecond dynamics of Cu(H2O)2 -: art. no. 054310

The ultrafast relaxation dynamics of Cu(H2O)(2) is investigated using femtosecond photodetachment-photoionization spectroscopy. In addition, stationary points on the Cu(H2O)(2) anion, neutral, and cation potential energy surfaces are characterized by ab initio electronic structure calculations. Electron photodetachment from Cu-(H2O)(2) initiates the dynamics on the ground-state potential energy surface of neutral Cu(H2O)(2). The resulting Cu(H2O)(2) complexes experience large-amplitude H2O reorientation and dissociation. The time evolution of the Cu(H2O)(2) fragmentation products is monitored by time-resolved resonant multiphoton ionization. The parent ion, Cu+(H2O)(2), is not detected above background levels. The rise to a maximum of the Cu+ signal from Cu-(H2O)(2), and the decay of the Cu+(H2O) signal from Cu-(H2O)(2) have similar tauapproximate to10 ps time dependences to the corresponding signals from Cu-(H2O), but display clear differences at very short and long times. The experimental observations can be understood in terms of the following picture. Prompt dissociation of H2O from nascent Cu(H2O)(2) gives rise to a vibrationally excited Cu(H2O) complex, which dissociates to Cu+H2O due to coupling of H2O internal rotation to the dissociation coordinate. This prompt dissociation removes all intra-H2O vibrational excitation from the intermediate Cu(H2O) fragment, which quenches the long time vibrational predissociation to Cu+H2O previously observed in analogous experiments on Cu-(H2O). (C) 2005 American Institute of Physics.