Laser photofragment spectroscopy of diatomic molecular ions

Abstract

High resolution (< 0.005 cm−1) electronic spectra of the diatomic molecular ions 70GeH+ and 74GeH+ have been recorded using a fast ion beam irradiated by a cw tunable dye laser. Over 150 transitions between the ground X1∑ + state and near-threshold levels of electronic states correlating to the lowest dissociation asymptotes Ge+(2P3/2) + H(2S) and Ge+(2P1/2) + H(2S) were observed in the range 16500 cm−1 to 18500 cm−1. The majority of the lines arise from a 1π-1∑ transition, where the predissociated excited state levels lie between the fine structure dissociation limits (Feshbach Resonances). The lifetimes of the rovibrational levels are found to increase, then decrease, with increasing rotational quantum number. Evidence for triplet (multichannel) mixing is revealed through the observation of additional lines and proton nuclear hyperfine splittings. Experimental results are compared with predictions of the vibrational and rotational energy levels obtained from a numerical solution of the Schrodinger equation. Least squares fitting yields molecular constants for the 1∑and the 1π states. A new apparatus used to create jet-cold molecular ions in a fast ion beam is detailed. Preliminary results have been obtained for the b4∑− g ← a4πu transition of O+ 2 which allow a rotational temperature for the source to be calculated