Rotational Analysis of the C2Π → X2Σ+ Electronic Transition of LaO

Abstract

A rotational analysis of the 0–0 band of the LaO C2Πr → X2Σ+ transition near 4400 Å has revised the previously reported analysis. It is demonstrated that the C2Π state is also the upper state of previously analyzed bands near 6500 Å. It is shown that the X state of LaO is 2Σ+ and that an interaction between the unpaired electron and the La nuclear spin causes a doubling (0.51 cm−1) of each rotational level. This splitting appears to show a slight rotational dependence and a negligible vibrational dependence. The coupling of the X2Σ+ state is nearly pure case bβS. The C2Πr state exhibits a large Λ doubling. The 0–0 subband origins are at 22 839.61 for the C2Π3/2 → X2Σ+ and 22 618.87 cm−1 for the C2Π1/2 → X2Σ+. Rotational spectroscopic constants are reported.