Knowledge Bank

Cavity RingDown Spectroscopy (CRDS) has been used to investigate the $b\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma g+-X3\Sigma g-$ system of oxygen isotopomers. The absorption bands of this system are very weak due to the strongly forbidden character of gerade-gerade and $\Sigma +-\Sigma -$ transitions, and they can only be observed via a magnetic dipole transition moment. The four allowed branches are a factor of $109$ weaker than typical electric dipole allowed transitions. The high sensitivity $(10-9cm-1)$, obtained even in a short cell , makes CRDS ideal for spectroscopy on isotopically enriched samples. Our studies yield updated or new values for the molecular constants of the $b\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma g+-X3\Sigma g-(v\prime ,0)$ bands for $v\prime =0.3$ of oxygen isotopomers. These values may help to identify emission bands from excited vibrational levels of $O2(b1\Sigma g+)$, including minority isotopomers, as observed in the Earth's $atmospherea$ and can aid in the interpretation of weak signals in the search for possible violation of the symmetrization postulate in $\mathrm{<mrow\; data-mjx-texclass="ORD">16</mrow>}O2\delta c$.