Rotational analysis of a new electronic transition of HBr and DBr

The authors report new observations at high resolution of the absorption spectra of HBr and DBr using synchrotron radiation as the background continuum source. The new spectra reveal overlapping rotational structure in the region 1100-1200 AA. They have been able to analyse the 1 Sigma - 1 Sigma + band originating from the ( sigma 2 pi 3 )6p pi configuration. Rotational constants have been determined for both HBr and DBr, and electronic configuration assignments are proposed for most of the bands between 1280 and 1100 AA.