# DIRECT STATE-SELECTIVE MEASUREMENT OF THE COOLING RATES OF VIBRATIONALLY EXCITED $1^{3}\Sigma^{+}_{g} Na_{2}$ ON THE SURFACE OF HELIUM CLUSTERS

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 Title: DIRECT STATE-SELECTIVE MEASUREMENT OF THE COOLING RATES OF VIBRATIONALLY EXCITED $1^{3}\Sigma^{+}_{g} Na_{2}$ ON THE SURFACE OF HELIUM CLUSTERS Creators: Reho, J.; Higgins, J.; Lehmann, K. K.; Scoles, G. Issue Date: 1998 Publisher: Ohio State University Abstract: Optical excitation of the $(v^{\prime} = 10)1^{3}\Sigma_{g}^{+}\leftarrow 1^{3}\Sigma^{+}_{a}$ transition of $Na_{2}$ formed on a He cluster surface yields dispersed emission which can only be modeled by including significant contributions from all $(v^{\prime} - 10)$ lower vibrational levels of the excited electronic state. The process by which this vibrational energy is transferred from the excited dimer to the He nanodroplet has been characterized using state-selective time-correlated single photon counting. We have measured the onset of fluorescence arising from lower $v^{\prime}$ levels upon excitation of various higher vibrational states and find that in all cases fluorescence begins in less than 250 ps. Along with the non-exponential nature of the distribution of level populations, this leads us to conclude that the vibrational energy is not transferred in a cascading process but rather by means of multiquanta jumps. Following the vibrational deexcitation, the dimer emits in the gas phase, having desorbed from the cluster surface. Description: Author Institution: Department of Chemistry, Princeton University URI: http://hdl.handle.net/1811/18887 Other Identifiers: 1998-RC-11