Spectroscopic constants and potential energy curves of Bi2 and Bi−2

The Dimethylbismuth Cation: Entry Into Dative Bi-Bi Bonding and Unconventional Methyl Exchange

The isolation of simple, fundamentally important, and highly reactive organometallic compounds remains among the most challenging tasks in synthetic chemistry. The detailed characterization of such compounds is key to the discovery of novel bonding scenarios and reactivity. The dimethylbismuth cation, [BiMe2 (SbF6 )] (1), has been isolated and characterized. Its reaction with BiMe3 gives access to an unprecedented dative bond, a Bi→Bi donor-acceptor interaction. The exchange of methyl groups (arguably the simplest hydrocarbon moiety) between different metal atoms is among the most principal types of reactions in organometallic chemistry. The reaction of 1 with BiMe3 enables an SE 2(back)-type methyl exchange, which is, for the first time, investigated in detail for isolable, (pseudo-)homoleptic main-group compounds.

Spectroscopic study of optical centers formed in Bi-, Pb-, Sb-, Sn-, Te-, and In-doped germanate glasses

We have shown that the broadband near-IR (NIR) fluorescence recently discovered in Bi-doped glasses is not specific due solely to Bi ions. Glasses doped with different 6p (Bi, Pb) and 5p (Sn, Sb) ions exhibit very similar behavior characterized by four major spectral peaks observed in two-dimensional excitation-emission plots and the lifetime of metastable level of about 400 micros. Our results challenge the existing models of optical centers in Bi-doped glasses. Point defect optical centers caused by the presence of 6p (Bi, Pb) and 5p (Sn, Sb) ions are proposed for the explanation of NIR emission in these laser materials.

Predissociation of Bi2 A(0u+), v′=21–39

Collisionless lifetimes for Bi2 A(0u+), v'=20-39, J'<or=105 have been measured using pulsed laser induced fluorescence techniques to investigate the effects of predissociation. The observed predissociation rates, Gamma=kpd(v')J(J+1), are quite rapid, ranging from kpd=1.53x10(2) s-1 for v'=21 to 1.5x10(5) s-1 for v'=39. The dense Bi2(A-->X) spectrum required both traditional lifetime measurements and synthetic spectrum fits to laser excitation spectra to determine the full range of observed rates. A single, repulsive potential responsible for the observed A-state predissociation could not be identified to adequately describe the vibrational dependence of the predissociation rates.

Superbroadband 1310 nm emission from bismuth and tantalum codoped germanium oxide glasses

Near-infrared broadband emission from bismuth-tantalum-codoped germanium oxide glasses was observed at room temperature when the glasses were pumped by an 808 nm laser diode. The emission band covered the O, E, S, C, and L bands (1260-1625 nm), with a maximum peak at approximately 1310 nm, a FWHM broader than 400 nm, and a lifetime longer than 200 micros. The observed broadband luminescence was attributed to bismuth clusters in the glasses. Bismuth-tantalum-codoped germanium oxide glass might be promising as amplification media for broadly tunable lasers and wideband amplifiers in optical communications.

Analysis of the Effect of Spin−Orbit Coupling on the Electronic Structure and Excitation Spectrum of the Bi22- Anion in (K-crypt)2Bi2 on the Basis of Relativistic Electronic Structure Calculations

The Bi2(2-) anions that have been characterized in (K-crypt)2Bi2 are isoelectronic with O2 but are diamagnetic and EPR-silent, unlike O2. The UV-vis spectrum measured for (K-crypt)2Bi2 shows two broad absorption peaks located at 2.05 and 2.85 eV, but no absorption at lower energies down to 0.62 eV. To account for these observations, the electronic structures of the isoelectronic diatomic dianions Q2(2-) (Q = N, P, As, Sb, Bi) were compared on the basis of relativistic density functional theory calculations, and the electronic excitations of Bi2(2-) were analyzed on the basis of relativistic configuration interaction calculations. The extent of spin-orbit coupling, brought about by the relativistic effect, increases steadily in the order N < P < As < Sb < Bi such that the "closed-shell" state is more stable than the "open-shell" state for Bi2(2-), while the opposite is the case for N2(2-), P2(2-), As2(2-), and Sb2(2-). The nature of the electronic excitations of Bi2(2-) was assigned and discussed from the viewpoint of molecular orbitals in the absence of spin-orbit coupling.

Laser Excitation Spectra and Franck-Condon Factors for Bi2 X1Sigma+g --> A(0(+)u)

Laser excitation spectra of the lowest vibrational levels, v" = 2-5 and v' = 0-4, for the Bi2 X1Sigma+g --> A(0(+)u) system have been recorded for a wide range of rotational levels, 0 < J < 211, at Doppler-limited resolution of 0.013 cm-1. New rotational term values and spectroscopic constants are reported, improving the accuracy of predicted line positions for high rotational levels by as much as 0.8 cm-1. In addition, Franck-Condon factors are computed and compared with experimental observations from CW laser-induced fluorescence spectra.