Knowledge Bank

\maketitle High resolution infrared emission spectra of hot BeF$2$in the 800--2500 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ region have been rotationally analyzed. The $\nu 3$ fundamental band, $\nu 1+\nu 2$, $\nu 1+\nu 3$ and $2\nu 2+\nu 3$ combination bands, and more than 15 hot bands were assigned. The $\nu 1$ ($\sigma g$), $\nu 2$ ($\pi u$) and $\nu 3$ ($\sigma u$) frequencies were directly obtained by fitting several hot bands and combination bands together. A complete analysis of all the bands is in progress and will be presented. High level ab initio calculations have been performed for the MgF$2$ molecule to predict its vibration-rotation spectrum. An infrared emission spectrum of MgF$2$ was recorded and will be assigned with the aid of ab initio calculations.