The A3Πi–X3Σ− emission systems of OH+ and OD+ have been reinvestigated in detail. Fourteen bands have been analyzed (of which seven are new), and accurate rotational constants have been obtained for the levels ν = 0–2 in the two states of OH+ and ν = 0–3 in the two states of OD+. Corrected assignments are given for the low J lines in the bands of OH+ (which are important in astrophysical spectra, such as those of H2O containing comets).The perturbations in the A3Π states of both isotopes have been studied quantitatively, and the erratic Λ doubling explained in detail. The position of the perturbing b1Σ+ state has been determined to within a few cm−1, and minor perturbations by the A1Δ state have been characterized. Values of the spin–orbit coupling constant, A, and the spin–spin interaction parameter, α, have been extracted from the data for OD+A3Π ν = 0.

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Rotational analysis of over 50 sub-bands of three emission transitions of 74GeF has given vibrational and rotational constants for the four lowest-lying electronic states of GeF. One of these is a 4Σ− state in Hund's case (a), where all four spin components have been identified. Extensive perturbations between this 4Σ− state and the B2Σ+ state have been analyzed in detail: the two states appear to interact mainly by a second-order mechanism through the so far uncharacterized σπ22Σ+ state, but the surprisingly large J dependence of the perturbation matrix element suggests that another mechanism, possibly involving the ground state, may contribute. Further perturbations, where the lines show an unusual intensity enhancement, appear in those sub-bands with B2Σ+ ν = 4 as upper state.

The relaxation dynamics of HCl, DCl, H 2 S, and D 2 S following photoexcitation in the vicinities of the Cl and S K-shell thresholds (ϳ2.8 keV for Cl, ϳ2.5 keV for S͒ were studied by means of ion time-of-flight mass spectroscopy. In all cases, the onset of pre-edge core-shell photoionization precedes the formation on resonance of a significant amount of neutral hydrogen as well as postcollision-interaction effects above threshold. Examination of the width of the H ϩ peak in spectra taken with the analyzer parallel and perpendicular to the polarization vector of the incident light indicates that on resonance, the photofragmentation asymmetry parameter, ␤, is approximately two for HCl, and is clearly positive for H 2 S. ͓S1050-2947͑98͒08211-0͔

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