Relativistic configuration interaction study of the low‐lying electronic states of Bi2

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.

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.

Ab initio Relativistic CI Calculations of the Spectroscopic Constants and Transition Probabilities for the Low-Lying States of the BiOH/HBiO Isomers

Spin-orbit MRD-CI calculations have been carried out for the potential energy surfaces of the seven lowest-lying electronic states of the BiOH molecule by employing relativistic effective core potentials. The HBiO isomer is found to be 4020 cm-1 less stable because of its inability to form multiple Bi-O bands. A bent 3A" BiOH ground state is predicted, which is split into all three of its components by spin-orbit coupling. The calculated X2A"-X1A' splitting is computed to be 5217 cm-1, but the corresponding X3-X2 value is only 29 cm-1. Fink et al. have observed spectral bands which appear with a Te value of 6200 cm-1 which are likely caused by BiOH. Since calculations at the same level for BiF underestimate the observed X2-X1 spin-orbit splitting by 650 cm-1, it appears that the present calculations are consistent with this experimental assignment. A vibrational progression with a 500 cm-1 frequency is also observed and this result fits in well with the computed Bi-O stretch omegae value of 527 cm-1. The calculations also find a relatively large 1Delta splitting (600 cm-1) because of the bent BiOH geometry, with comparatively strong transitions to the X1A' ground state, and it is suggested that the experimental BiOH assignment can be confirmed on this basis. Much stronger transitions to the 1Delta component should also be observed in emission in the 10 000 cm-1 range. Copyright 1997 Academic Press. Copyright 1997Academic Press