THE GEOMETRY AND INTERMOLECULAR BINDING OF HCN...BRCL PROBED BY ROTATIONAL SPECTROSCOPY

Ground-state rotational spectra of several isotopomers of a linear com plex formed between HCN and BrCl were observed by pulsed-nozzle, F-T m icrowave spectroscopy and analysed to give the spectroscopic constants B-0, D-J, chi(Br), chi(Cl), and M(bb)(Br). The order HCN...BrCl of th e nuclei was established from the changes in the B-0 values on isotopi c substitution. The small fractional electronic charge (delta = 0.05) transferred from Br to Cl on complex formation and the intermolecular stretching force constant (k(sigma) approximate to 11 N m(-1)) estimat ed from the spectroscopic constants indicates a weak interaction of HC N and BrCl, with little perturbation of the charge distribution of BrC l.