Knowledge Bank

Tellurium (Te$2$) is widely used as a frequency reference, largely due to the fact that it has an optical transition roughly every 2-3 GHz throughout a large portion of the visible spectrum. Although a standard atlas encompassing over 5200~cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ already exists [1], Doppler broadening present in that work buries a significant portion of the features [2]. More recent studies of Te$2$ exist which do not exhibit Doppler broadening, such as Refs. [3-5], and each covers different parts of the spectrum. This work adds to that knowledge a few hundred transitions in the vicinity of 444~nm, measured with high precision in order to improve measurement of the spectroscopic constants of Te$2$'s excited states. Using a Fabry Perot cavity in a shock-absorbing, temperature and pressure regulated chamber, locked to a Zeeman stabilized HeNe laser, we measure changes in frequency of our diode laser to $\sim$1 MHzprecision.Thisdiodelaserisscannedover1000GHzforuseinasaturated-absorptionspectroscopycellfilledwithTe$_2$ vapor. Details of the cavity and its short and long-term stability are discussed, as well as spectroscopic properties of Te$2$. \ References: \begin{enumerate} \item J.~Cariou, and P.~Luc, \newblock \emph{Atlas du spectre d'absorption de la molecule de tellure}, Laboratoire Aime-Cotton (1980). \item J.~Coker et~al., \newblock J. Opt. Soc. Am. B {\bf 28}, 2934 (2011). \item J.~Verges et~al., \newblock Physica Scripta {\bf 25}, 338 (1982). \item Ph.~Courteille et~al., \newblock Appl. Phys. B {\bf 59}, 187 (1994) \item T.J.~Scholl et~al., \newblock J. Opt. Soc. Am. B {\bf 22}, 1128 (2005). \end{enumerate}