Knowledge Bank

Improved molecular constants for $\mathrm{<mrow\; data-mjx-texclass="ORD">12</mrow>}C16O$, $\mathrm{<mrow\; data-mjx-texclass="ORD">12</mrow>}C18O$, $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}C16O$, and $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}C18O$ have been determined by using a heterodyne technique to measure beat frequencies up to 46 GHz between $\mathrm{<mrow\; data-mjx-texclass="ORD">12</mrow>}C16O$ and frequency-doubled $CO2$ lasers and between $\mathrm{<mrow\; data-mjx-texclass="ORD">12</mrow>}C16O$ and rare-isotope CO lasers.