Experimental and theoretical study of the electronic states and spectra ofBiNa

Gas-phase emission spectra of the hitherto unknown free radical BiNa have b een measured in the NIR range with a Fourier transform spectrometer. The em issions were observed from a fast-flow system in which bismuth vapor in arg on carrier gas was passed through a microwave discharge and mixed with sodi um vapor in an observation tube. Two systems of blue-degraded bands observe d in the ranges 8900-9800 and 7200-7800 cm(-1) were measured at high spectr al resolution and vibrational and rotational analyses were performed. To ai d in the analysis of the experimental data, a series of relativistic config uration interaction calculations has been carried out to obtain potential c urves for the low-lying states of BiNa and also electric dipole transition moments connecting them. As in the isovalent BiH system, the ground state o f BiNa is found to be X(3)Sigma (-) with a spin splitting of about 1769 cm( -1). The first excited stale is A(3)Pi, and the observed band systems are a ssigned to the transitions A(3)Pi (A(2)O(+)) --> X(3)Sigma (-)(X(1)0(+), X( 2)1). Comparison with earlier work on the isovalent BiH system emphasizes t hat the relative weakness of the a MO in BiNa is responsible for qualitativ e differences in the electronic spectra of these two systems. (C) 2000 Acad emic Press.