High-resolution analysis of the ν4 absorption band of CH279BrF

The gas-phase infrared spectrum of the nu(4) fundamental band of (CH2BrF)-Br-79 was recorded in the 1010-1116 cm(-1) wavenumber region using a TDL spectrometer. In this first high-resolution investigation of the synthesized Br-79 isotopic form, more than 10 200 transitions of this alb-hybrid band centered at 1068.5385 cm(-1) were assigned and, using the Watson's A-reduced Hamiltonian in the I'-representation, a reliable set of molecular constants for the excited state nu(4) = 1 was determined, From ground state combination differences having rotational quantum numbers J and K-a up to 97 and 21, respectively, improved and extended ground state rotational and centrifugal distortion constants were calculated as well. Comparison between the observed and calculated band intensities in appropriate regions of the spectrum gave an estimate of the transition dipole-moment ratio along the a and b axes as [Delta mu(a)/Delta mu(b)] = 2.0 +/- 0.2, in agreement with the predicted theoretical value of 1.99. (C) 2000 Academic Press.