The B1Pi --> X1Sigma+ System of Scandium Monoiodide.

Rotational analyses have been carried out on eight thermically excited emission bands of the infrared B1Pi --> X1Sigma+ system of scandium monoiodide between 4000 to 5000 cm-1, recorded by Fourier transform spectrometry. Rotational constants and energies are obtained for X1Sigma+ (v = 0, 1, 2) and B1Pi (v = 0-4) levels from which equilibrium constants of the states are derived. Perturbational effects are observed in the bands with v" = 1 that are interpreted as consequences of the avoided crossing of X1Sigma+ (v = 1) and a3Delta1 (v = 0) at J = 70. A treatment of the perturbation is made using an effective 2 x 2 matrix representation of the rotational energies of the two levels. Copyright 1998 Academic Press.