Fluorescence excitation and depletion spectroscopy of the BAr complex: Electronic states correlating with the excited valence B(2s2p2 2D) asymptote

Abstract

Laser fluorescence excitation and depletion spectra of the BAr van der Waals complex, in the spectral region around the B atomic 2s2p2 2D←2s22p 2P transition at 208.9 nm, are reported. The fluorescence excitation spectrum displays a series of structured bands, whose excited levels are weakly bound (⩽60 cm−1), and an unstructured continuum to the blue. The onset of the latter allows determination of the ground state dissociation energy D0″=102.4±0.3 cm−1. The fluorescence depletion spectrum reveals, in addition, bands at lower wave numbers to a strongly bound, predissociating state, assigned as C2Δ. The bands observed by fluorescence excitation are assigned to the D2Π, E2Σ+–X2Π transitions. The derived spectroscopic data are used to construct potential energy curves for the C2Δ and D2Π states. The predissociation of the C2Δ state is due to spin–orbit coupling to a repulsive 4Π state correlating with the B(2s2p2 4P)+Ar asymptote, as shown in the accompanying paper [K. Sohlberg and D. R. Yarkony, J. Chem. Phys. 106, 6607 (1997)]. A weak nonradiative decay process is also observed for the D2Π state.