Ab initio and high resolution infrared study of FC CBr

High-level ab initio calculations with large basis sets are reported for br omofluoroethyne, FCCBr. Based on CCSD(T) results, an empirically corrected theoretical equilibrium geometry is derived. Correlated harmonic (CCSD(T)) and anharmonic (MP2) force fields provide theoretical predictions for the f undamental vibrational wavenumbers and many other spectroscopic constants. The experimental section describes a new synthesis of FCCBr by pyrolysis of 2-bromo-1,3-difluoro-4,5,6-triazine, High resolution infrared spectra are recorded and analyzed in the region between 100 and 2500 cm(-1). All fundam ental bands except was well as several combination, overtone, and hot bands are observed. The molecular parameters derived from these spectra are in e xcellent agreement with the ab initio results. (C) 1999 Elsevier Science B. V. All rights reserved.