Knowledge Bank

Direct measurements of the lowest pure rotational transitions of the $\Omega$ = 7/2, 5/2, and 3/2 ladders of FeD and of the $\Omega$ = 1/2 ladder of FeH in the $\mathrm{<mrow\; data-mjx-texclass="ORD">4</mrow>}\Delta i$ ground electronic states have been conducted using millimeter/sub-millimeter direct absorption techniques in the frequency range 530-810 GHz. Both species were created in an AC discharge from the reaction of Fe(CO)$\mathrm{<mrow\; data-mjx-texclass="ORD">5</mrow>}$ with H$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ or D$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$. In several of these transitions lambda-doubling and proton/deuterium hyperfine structure have been resolved. These data improve on the zero field frequencies predicted from previous LMR data by several MHz. Accurate frequencies are crucial for sub-millimeter searches for FeH toward the interstellar medium. Searches for additional transitions are in progress. \ \ J.M. Brown, H. Korsgen, S.P. Beaton, &amp; K.M. Evenson, J. Chem. Phys. 124, 234309 (2006)