VIBRATIONAL AND ROTATIONAL STRUCTURE IN THE HEI-EXCITED PHOTOELECTRON-SPECTRUM OF THE A(2)SIGMA(+)(1/2) STATE OF HBR+

The A (2) Sigma(1/2)(+) state of HBr+ has been studied experimentally using HeI photoelectron spectroscopy and theoretically employing an ab initio multireference configuration-interaction method. Vibrational structure has been observed throughout the band up to the dissociation limit. The vibrational lines corresponding to v = 3-9 are much broadened due to strong interaction with repulsive states as found in earlier studies. In recordings with a resolution of about 4-5 meV, rotational structure has been observed for the v = 0, 1, 2, 11, 12, and 13 vibrational states. The spectra have been fitted using calculated rotational constants. It is found that the Delta N = +/- 1 branches dominate the photoelectron bands but also the Delta N = +/- 3 transitions are significant. For the lowest states the T branch (Delta N = 3) forms a well-separated band.