Electric charge redistribution in BrCl resulting from interaction with Ar: the rotational spectrum of the linear complex Ar⋯BrCl

Ground-state rotational spectra of four isotopomers Ar⋯79Br35Cl, Ar⋯81Br35Cl, Ar⋯79Br37Cl and Ar⋯81Br37Cl of a complex involving argon and bromine monochloride were observed. Spectroscopic constants were interpreted on the basis of a linear species Ar⋯BrCl, with atoms in the indicated order and r(Ar⋯Br)=3.466 Å. When intermolecular electron transfer was assumed negligible, the Br and Cl nuclear quadrupole coupling constants were interpreted to show that a fraction δ(Br→Cl)=3.5(5)×10−3 of an electron is transferred from Br to Cl on complex formation. The values kσ=2.79(1) N m−1 and kββ=4.7(2)×10−20 J rad−2 were established for the intermolecular stretching and bending quadratic force constants, respectively.