15min:

N. T. HUNT, W. Y. FAN, Z. LIU AND P. B. DAVIES, Department of Chemistry, Uiversity of Cambridge, Cambridge CB2 1EW, UK.

Infrared absorption spectra of ¹¹B⁷⁹Br, ¹¹B⁸¹Br, ¹⁰B⁷⁹Br and ¹⁰B⁸¹Br have been observed between 650 and 720 cm^-1 in a BBr₃/He ac discharge using diode laser spectroscopy. Over 200 lines consisting of both fundamental and hot bands up to v''=5 have been fitted to Dunham expansions. The fitted parameters are used to derive the vibrational constants of ¹¹B⁷⁹Br, \omega_e=685.1844(17) cm^-1 and \omega_ex_e=3.7347(11) cm^-1. The equilibrium dissociation energy is also obtained from expanded Dunham-Morse potential, D_e=32647(49) cm^-1.