SPIN-ORBIT CONFIGURATION-INTERACTION STUDY OF THE ELECTRONIC-SPECTRUMOF ANTIMONY IODIDE

Relativistic effective core potentials (RECPs) have been employed in t he framework of a spin-orbit configuration interaction (CI) approach t o compute potential energy curves for the lowest-lying electronic stat es of the SbI molecule, as well as the Einstein coefficients of sponta neous emission for transitions between them. In contrast to systems su ch as arsenic and antimony fluoride, it is found that the lowest (II)- I-3 state of SbI is repulsive, and a qualitative explanation for this distinction in terms of the electronegativity difference of the consti tuent atoms is put forward. The computed T-e value of the a (1) Delta( 2) state is in good agreement with a result inferred on the basis of e xperimental b 0(+) and a (1) Delta(2) T-e values in other group VA-VII A and VIA-VIA systems. Two different semicore and full-core RECPs have been employed at various levels of sophistication in the spin-orbit C I treatment to obtain the present results and the corresponding findin gs are in generally good agreement with one another. The intensity of the b-X(1) transition is computed to be much larger than that of b-X(2 ), in agreement with the observations of Winter et al. The fact that t he opposite relationship has been found for SbF and many other diatomi cs in which the halogen is the lighter of the two atoms, as first poin ted out by Colin et al., is discussed and also found to be closely tie d up with electronegativity considerations.