Rotational analysis of the red electronic emission system A3[Phi] --> X3[Delta] of diatomic niobium nitride (NbN)

Abstract

The (0,0) band of the red emission system of the diatomic molecule niobium nitride (NbN) has been rotationally analyzed and found to arise from an A3[Phi]r-X3[Delta]r transition. Constants for the two states have been determined including the magnitude of the spin-orbit coupling constants in spite of their strong numerical correlation: The electronic states involved belong to case (a) coupling and no satellite bands are observed. That these results are consistent with those of similar molecules such as ZrO and TiO is verified. The asymmetry of the energy separations of the three subsystems 3[Phi]4-3[Delta]3, 3[Phi]3-3[Delta]2, and 3[Phi]2-3[Delta]1 probably has its main origin in the perturbation of the X3[Delta]2(5[sigma]4d[delta]) substate by the low-lying 1[Delta] state of the same electronic configuration. A significant line broadening for J > 60, particularly in the 3[Phi]2-3[Delta]1 (0,0) subband, has been found. It is attributed to [Lambda] doubling or hyperfine broadening due to spin uncoupling but has not been definitively analyzed at this time. No localized perturbations have been found in any of the subbands.