ABSTRACT
Slow electron velocity map imaging (SEVI) spectroscopy was used to examine the BeS- anion to neutral ground-state transition, X 2Σ+ â X 1Σ+. Rotational constants, vibrational intervals, and the electron binding energy of BeS- were determined. Partially resolved rotational contours were seen due to the relatively small moment of inertia of beryllium sulfide. Upon analysis of the rotational contours, it was found that changes in the molecular rotational angular momentum, ΔN = -1, -2, -3, and -4, facilitated photodetachment at near-threshold photon energies. The electron affinity of BeS was found to be 2.3346(2) eV. SEVI spectra recorded using photon energies near the threshold for Δv = -1 processes exhibited features that were associated with a dipole-bound state (DBS) of BeS-. Autodetachment spectroscopy was used to probe this state, and rotationally resolved data were obtained for the DBS 2Σ+, v' = 0 - X 2Σ+, vâ³ = 0 transition. Analysis of this structure provided the rotational constants for BeS- X, vâ³ = 0, and the electron binding energy of the DBS. Electronic structure calculations, performed at the RCCSD(T) and MRCI levels of theory, gave predictions that were in good agreement with the experimental observations.
ABSTRACT
The X2Σ+âX1Σ+ anion to neutral ground state photodetachment of BeO- has been studied by means of photoelectron velocity-map imaging spectroscopy in a newly constructed apparatus. Vibrational intervals, rotational constants, and the electron detachment threshold of BeO- were determined for the first time. The small moment of inertia of beryllium oxide allowed for the observation of partially resolved rotational contours. Analyses of these contours provided evidence of several detachment channels resulting from changes in molecular rotational angular momenta of ΔN = 0, ±1, ±2, and ±3. The relative intensities of these detachment channels were found to be a function of the electron kinetic energy. Experimental results are compared to the predictions of high level ab initio calculations.
