Knowledge Bank

We have recorded the vibration-rotation spectra of gaseous MgH and $MgH2$ in emission using a furnace-discharge source. The molecules were generated at $650\circ C$ and 333 mA discharge current with magnesium and a mixture of argon and hydrogen gases. The recorded spectra contained several emission bands, as well as the absorption of atmospheric $H2O$. The highest signal-to-noise ratio for MgH lines was about 200. Three vibrational bands, $v=1-0$ to $v=3-2$, for $\mathrm{<mrow\; data-mjx-texclass="ORD">24</mrow>}MgH$ and two vibrational bands for $\mathrm{<mrow\; data-mjx-texclass="ORD">25</mrow>}MgH$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">26</mrow>}MgH$ were observed in the $2\Sigma +$ ground electronic state. The analysis of the infrared data combined with our previous data on the $B\prime -X$ electronic transition will lead to an improved potential energy curve for the ground state using a direct-potential-fit approach. In addition to MgH, we found the antisymmetric stretching mode $(\nu 3)$ of $\mathrm{<mrow\; data-mjx-texclass="ORD">24</mrow>}MgH2$ and three hot bands involving $\nu 2$ and $\nu 3$ in our spectrum. The bands were rotationally analyzed and the spectroscopic constants were determined. The $MgH2$ molecule has a linear structure with an $R0$ Mg-H bond length of $1.703327(3)\backslash AA$.