MOLECULAR BEAM-LASER SPECTROSCOPY OF THE $NeCl_{2}$ VAN DER WAALS MOLECULE

Address of Evard, Cline, and Janda: Chemistry Building, University of Pittsburgh, Fittsburgh, PA 15260. Address of Thommen: CIBA-Geigy, Basel, Switzerland.Author Institution:The $B^{3}{\Pi_{0}}_{g}^{+} - X^{1}\Sigma_{g}^{+}$ systems of $Cl_{2}$ and the associated van der Waals molecule $NeCl_{2}$ formed in a molecular beam have been studied by laser induced fluorescence. Twelve $bands^{2}$ originating from $X(v^{\prime}=0,1)$ have been observed at $0.02 cm^{-1}$ laser resolution and one band, $B-X (9-1)$ has been examined at $0.001 cm^{-1}$ laser resolution. The experimental resolution is limited by Doppler broadening and by the homogeneous linewidth of the transition, due to vibrational predissociation, which are on the same order. The excitation spectra were simulated by a model consisting of a T-shaped rigid rotor Hamiltonian for both the ground and excited electronic states. The vibrational predissociation lifetimes, extracted by convolution of the linewidths, range from 29.2 ps for $NeCl_{2} B(v^{\prime\prime}=13)$ to 664 ps for $NeCl_{2} B(v^{\prime\prime}=7)$. The lifetimes obtained from the lower resolution work agree well with that found in the high resolution spectrum, but the high resolution spectrum is necessary to accurately determine the structural parameters