Theoretical study of the low-energy BiN spectrum

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