Knowledge Bank

The laser induced fluorescence spectrum of jet-cooled CoC has been measured at high resolution following the reaction of laser-ablated cobalt atoms with methane. The $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Sigma +$ ground state is an unusually good example of Hund's case $(b\beta S)$ coupling. Since $\mathrm{<mrow\; data-mjx-texclass="ORD">59</mrow>}Co$ has a nuclear spin l = 7/2, each rotational level is split by the Fermi contact interaction into G = 3 and 4 components, where G = I + S; the splitting is roughly 4b, and for N = 0 is more than $0.5cm-1$. The $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Sigma +$ state begins to uncouple toward case $(b\beta J)$ at higher N values. We have identified three upper state $\Pi$ levels giving rise to bands at $13078cm-1(\Omega =3/2),13344cm-1(\Omega =1/2)$ and $13428cm-1(\Omega =3/2)$; only transitions to the first two are strong enough to be recorded at high resolution. There are three more $\Pi$ levels approximately $1000cm-1$ higher in energy. Furthermore, we have identified a very low-lying $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Delta i$ state, for which the $\Omega =5/2$ and 3/2 levels lie at 222 and $1173cm-1$, respectively. Laser excitation of the $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Pi 3/2-\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Delta 5/2$ transition has been observed by monitoring the strong $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Pi 3/2-\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Sigma +$ emission, which has allowed the $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Delta 5/2$ state to be characterized at high resolution. A total of 879 hyperfine transitions between the various $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Pi 1/2,\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Pi 3/2\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Delta 5/2$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Sigma +$ states has been assigned and fitted. The $\Pi$ and $\Delta$ states were treated with a case (c) model and the $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Sigma +$ state in case $(b\beta S)$, following the full derivation of the appropriate matrix elements.