Rotational spectrum of a salt-containing van der Waals complex: Ar-NaCl

The first spectroscopic identification of a van der Waals complex containing salt, Ar-NaCl, has been reported. A cm-region rotational spectrum of the complex has been observed for the ³⁵Cl and ³⁷Cl isotopomers by using a Fourier-transform microwave spectrometer combined with a laser ablation nozzle source. The vibrationally averaged geometry of the complex is of the linear Ar⋯Na-Cl configuration, with the internuclear distance of R(Ar⋯Na)=2.887 Å. An almost fully resolved hyperfine structure in low-J transitions has yielded precise nuclear quadrupole coupling constants associated with both Na and Cl nuclei, which indicate a substantial charge rearrangement in the NaCl molecule by complexation with Ar.