Photoacoustic vibration-rotation overtone spectrum of the 4ν1 band system of monobromoacetylene

A high-resolution vibration-rotation overtone spectrum of natural monobromoacetylene (HCCBr) has been recorded with a titanium:sapphire ring laser spectrometer in the wave number region 12520–12840 cm−1. The main band assigned as 4ν1, its accompanying hot bands and some overtone bands have been rotationally analysed. Altogether nine vibrational bands belonging to the HCC79Br and eleven bands belonging to the HCC81Br isotopic species have been observed. Vibrational assignments for most of the vibrational bands have been obtained by employing a simple Fermi resonance model based on normal coordinates.