Knowledge Bank

Dispersed fluorescence spectroscopy of PdC in a supersonic expansion has led to the observation of five electronic states. These include the $12\sigma 2,1\Sigma +$ ground state and the set of four $12\sigma 16\pi 1,3\Pi \Omega$ states. Previous studies in this $laboratorya$ had determined the ground state to be $\Omega -0$; however, the dispersed fluorescence data presented here leads to the assignment of the ground state as $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma +$. Vibrational progressions have also been observed in the $12\sigma 2,1\Sigma +$; and $12\sigma 16\pi 1,3\Pi 0+$ states. These give values of $850.46\pm 3.55cm-1$ and $788.38\pm 5.35cm-1$, respectively. The previously observed $[17.9]\Omega =1statee$ is also identified as the $12\sigma 113\sigma 1,3\Sigma 1\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ state. Together with the dispersed fluorescence studies of $MoCb$ and $RuCe$, results from work on PdC are combined with characteristics of other carbides to illustrate relationships and trends between electronic configuration, ground state and low-lying state symmetry, and vibrational frequency.