Laser photofragment and emission spectroscopy of theA2Δ-X2Π system of PH+

The 1–2 band and part of the 0–1 band of the A 2Δ-X 2Π system of the PH+ molecular ion have been recorded in a laser/ion beam experiment. The spectra were obtained by the detection of P+ ions arising from predissociation of rotational levels of the A 2Δ state which lie above the lowest dissociation limit, P+(3 P) + H(2 S). The measured transition frequencies were merged with previously published emission lines for the 0-0, 0–1 and 1-0 bands and some remeasurements of the 0–1 band to yield a set of molecular parameters for the v = 0, 1 and 2 levels of the X 2Π state and the v = 0 and 1 levels of the A 2Δ state. From the sharp onset of lines in the predissociation spectrum at N = 13 of A 2Δ(v = 0), an upper limit for the dissociation energy D 0(2Π) of 3·369 eV is determined. The predissociation mechanism and astrophysical considerations are discussed.