Hydrogen Dibromide Radical: Infrared Detection through the Matrix Isolation Technique

Abstract

When hydrogen bromide–bromine–argon mixtures are passed through a glow discharge and the products are condensed at 20°K, prominent absorptions appear at 727.4, 892.1, and 1053.0 cm−1. With deuterium, these features shift to 496.1, 666, and 833 cm−1. Both deuterium and bromine isotope shifts show that these features can be assigned to the BrHBr (BrDBr) free radical in a linear, symmetric (D∞h) structure with ν3 = 727.4 (496.1) cm−1 and ν1 = 164.7 (170) cm−1. The evidence that these bands are not due to HBr2− is reviewed. The vibrational potential function for ν3 includes a large quartic term and it suggests that the hydrogen bond in HBr2 is comparable in strength to that in HBr2−.