Knowledge Bank

Submillimeter-wave rotational spectra of O$\mathrm{<mrow\; data-mjx-texclass="ORD">18</mrow>}$O and $\mathrm{<mrow\; data-mjx-texclass="ORD">18</mrow>}$O$2$ in the $a1\Delta g$ state have been detected in a new static discharge cell useful for studying rare isotopologues of transient molecules. Rotational transition frequencies of both species have been measured through 1.6 THz, to better than 1 part in $107$, allowing precise determination of molecular constants. The first measurements with our static discharge cell provide a check on the isotopic predictions in the $a1\Delta g$ state.