MILLIMETER-WAVE SPECTROSCOPY OF MgI (~X2Σ+)

The pure rotational spectrum of MgI in its ground electronic state (~{X}$^{2}$$Sigma$$^{+}$) has been measured using millimeter/submillimeter wave direct-absorption techniques. Rotational transitions arising from the v = 0, 1, and 2 vibrational states of $^{24}$MgI, as well as the v = 0 state for the isotopologues ($^{25}$MgI and $^{26}$MgI), have been measured in their natural abundance in the region of 200 – 300 GHz. Rotational, centrifugal distortion, and spin-rotation constants were determined for each isotopologue and the excited vibrational states of $^{24}$MgI. Equilibrium parameters B$_{e}$, $alpha$$_{e}$, D$_{e}$, and $gamma$$_{e}$ were ascertained and used to calculate an equilibrium bond length (r$_{e}$) for MgI. The spin-rotation coupling constants of several magnesium monohalides were examined and the contribution to the spin-rotation parameter appears to be dominated by second order spin-orbit coupling of the nearby excited A$^{2}$$Pi$ electronic state