EXPERIMENTAL DETERMINATION OF THE BINDING ENERGIES OF THE T-SHAPED AND LINEAR ISOMERS OF THE $Ne\cdots ICl(X,\nu^{\prime\prime} = 0)$ VAN DER WAALS COMPLEX
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Date
2004
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Publisher
Ohio State University
Abstract
Multiple features associated with transitions of the near T-shaped and linear $Ne\cdots I^{35,37}Cl(X,\nu^{\prime\prime} = 0)$ isomers are observed in laser-induced fluorescence spectra recorded in the $ICl B-X$, $2-0$ and $3-0$ spectral regions. The T-shaped complexes access the lowest intermolecular vibrational level within the $Ne + ICl(B, \nu^{\prime})$ potential, while the linear complexes access at least four different bending levels that are delocalized in the angular coordinate. The ground state binding energy of the linear $Ne\cdots I^{35}Cl$ isomer is directly measured in two-laser, action spectroscopy experiments. A continuum signal is observed with a turn on at $17 748.4 cm^{-1}$ that indicates a binding energy of $84.3(2.3) cm^{-1}$ for the ground state complex. The ground state binding energy of the T-shaped isomer can be estimated by fitting the $Ne\cdots I^{35}Cl(B,\nu^{\prime} = 2)$ bending levels that the ground state linear isomer accesses to an $\omega_{e}, \omega_{e}\chi_{e}$ progression. The fit reveals a binding energy of $60.8(3.2) cm^{-1}$ for $Ne\cdots I^{35}Cl(B,\nu^{\prime} = 2)$, which implies a T-shaped ground state binding energy of $66.2(3.2) cm^{-1}$ based upon the spectroscopic shift of the T-shaped feature from the $I^{35}Cl B-X, 2-0$ transition. Two-laser, pump-probe experiments were also performed to access the intermolecular vibrational levels that are bound within the $Ne + ICl(E0^{+}, \nu = 10)$ ion-pair state. In these experiments, the pump laser was fixed on either the lowest energy level, with a T-shaped equilibrium geometry, or one of the higher energy delocalized levels within the $Ne + I^{35}Cl(B,\nu^{\prime} = 2)$ well. In this manner, varying $Ne\cdots I^{35}Cl$ Franck-Condon windows between the B and E states are accessed and assignments of the intermolecular vibrational levels within the ion-pair state can be made. The results suggest a $Ne + ICl(E 0^{+})$ potential with the lowest bound level localized in the T-shaped orientation and that the higher energy levels are delocalized in the angular coordinate.
Description
Author Institution: Department of Chemistry, Washington University; Department of Chemistry, The Ohio State University