Rotationally resolved spectrum of the (A)over-tilde(060)-(X)over-tilde(000) band of HCBr

The rotationally resolved spectrum of the (060)(0)-(000) band in the A(1)A(")-X(1)A(') system of HCBr has been recorded in absorption using a frequency-modulated c.w. tunable dye laser. Both Br-79 and Br-81 isotopomer spectra were rotationally assigned and effective rotational constants determined. The spectrum contains both perpendicular and parallel rotational sub-band structures. The latter are partially due to axis-switching in the transition and Coriolis coupling in the excited state, but are relatively more intense and show a different J-dependence to that expected on the basis of these mechanisms. Intensity borrowing from a predicted but unobserved shorter wavelength transition explains the observations. We have calculated the energy and structure of HCBr in the state at the MRCI/cc-pVTZ level and find T-e(B-X) = 20908 cm(-1). The B-X band system should be experimentally observable. (c) 2005 Elsevier Inc. All rights reserved.