Experimental and Theoretical Study of the Electronic States and Spectra of BiNa

Abstract

Gas-phase emission spectra of the hitherto unknown free radical BiNa have been measured in the NIR range with a Fourier transform spectrometer. The emissions were observed from a fast-flow system in which bismuth vapor in argon carrier gas was passed through a microwave discharge and mixed with sodium vapor in an observation tube. Two systems of blue-degraded bands observed in the ranges 8900–9800 and 7200–7800 cm−1 were measured at high spectral resolution and vibrational and rotational analyses were performed. To aid in the analysis of the experimental data, a series of relativistic configuration interaction calculations has been carried out to obtain potential curves for the low-lying states of BiNa and also electric dipole transition moments connecting them. As in the isovalent BiH system, the ground state of BiNa is found to be X3Σ− with a spin splitting of about 1769 cm−1. The first excited state is A3Π, and the observed band systems are assigned to the transitions A3Π(A20+) → X3Σ−(X10+, X21). Comparison with earlier work on the isovalent BiH system emphasizes that the relative weakness of the ς MO in BiNa is responsible for qualitative differences in the electronic spectra of these two systems.