Electronic Spectroscopy of B Atoms and B2 Molecules Isolated in Para-H2, Normal-D2, Ne, Ar, Kr, and Xe Matrices

Abstract

We report spectroscopic observations on B atoms isolated in cryogenic parahydrogen (pH2), normal deuterium (nD2), Ne, Ar, Kr, and Xe matrices, and of B2 molecules in Ne, Ar, Kr, and Xe matrices. The 2s23s(2S)←2s22p(2P) B atom Rydberg absorption suffers large gas-to-matrix blue shifts, increasing from +3000 to +7000 cm−1 in the host sequence: Xe<Kr<Ar≈Ne≈nD2≈pH2. Much smaller shifts are observed for the 2s2p2(2D)←2s22p(2P) B atom core-to-valence transition. We assign pairs of absorption peaks spaced by ≈10 nm in the 315–355 nm region to the B2 (A 3Σu−←X 3Σg−) Douglas–Herzberg transition. We assign a much weaker progression in the 260–300 nm region to the B2 (2)3Πu←X 3Σg− transition. We report a novel progression of strong peaks in the 180–200 nm region which we suspect may be due to B2 molecules, but which remains unassigned. Ultraviolet (UV) absorption spectra of B/pH2 solids show two strong peaks at 216.6 and 208.9 nm, which we assign to the matrix perturbed 2s23s(2S)←2s22p(2P) and 2s2p2(2D)←2s22p(2P) B ...