Spectroscopic observation of the preferentially stabilized, linear He⋯ICl(X 1Σ+) complex

Abstract

Spectroscopic features attributed to rovibronic transitions from both the T-shaped and linear He⋯I35Cl(X) and He⋯I37Cl(X) ground-state complexes have been recorded in the ICl B 3Π0+–X 1Σ+, 2–0 and 3–0 spectral regions using laser-induced fluorescence spectroscopy. Experiments performed using varying expansion conditions indicate that the He⋯I35,37Cl(X) complex with a linear equilibrium orientation lies lower in energy than the separately localized T-shaped isomer even though the transition energies of the T-shaped and linear complexes are shifted by ∼3.5 and ∼14 cm−1 to higher energy than the I35,37Cl B–X band origins, respectively. Based on comparison with the excited state theoretical predictions of Waterland et al. [J. Chem. Phys. 92, 4261 (1990)], estimates of the binding energies for the ground state T-shaped and linear He⋯I35Cl(X) complexes are 17 and 21 cm−1, respectively, in qualitative agreement with the recently published predictions of 15.2 and 18.3 cm−1 obtained using high level ab initio theory for the ground state potential energy surface [J. Chem. Phys. 117, 7017 (2002)].