Knowledge Bank

A hyperfine analysis of the sub-Doppler intermodulated fluorescence spectrum of gaseous nioblum nitride (NbN) from 5700 {\AA} to 6300 {\AA} has been completed. Two triplet systems, the $\delta \pi 3\Phi -\sigma \delta X3\Delta$ in the orange region and the $\delta \pi 3\Pi -\sigma \delta X3\Delta$ in the yellow region have been studied. Both systems show very impressive hyperfine splittings due to the interaction between the $I=9/2$ nuclear spin of Nb and a metal centred unpaired electron. Severe perturbations occur in the energies of the spin-orbit components. It has been necessary to fit the ground state to a modified form of the case (a***) Hamiltonian where the isotropic hyperfine parameters in the matrix elements off-diagonal in $\Omega$ are treated as independent variables. The $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi$ state could only be fitted using a case (c) model. In addition, two new band systems near 8000 {\AA}, assigned as $\delta \pi \mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi -\delta 2\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Sigma -$ and $\delta \pi 3\Pi -\sigma \delta \mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Delta$, have been discovered by state-selected wavelength-resolved fluorescence. Preliminary analyses have been completed. Even though all the triplet states known are in good case (a) coupling, it has been possible to obtain their spin-orbit intervals through the observation of extremely weak spin satellite branches recorded at low resolution by wavelength-resolved fluorescence.