Knowledge Bank

Structured absorption has been observed while probing a $\mathrm{<mrow\; data-mjx-texclass="ORD">199</mrow>}$ Hg cell with a single frequency laser. The probe beam is sum-frequency generated using the technique of Blit $etal1$, but with the parent $Ar+$ and dye lasers operated single mode. The beam passes twice through a 50cm cell. Atomic absorption at the $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}So-3Po$ forbidden transition ($\sigma \simeq 1.2\times 10-20cm2$) is observed as well as many rotational lines of the $Og+-1u$ system. These lines, occurring with ca. 4 GHz spacing, are believed to be the first observation of resolved rotational structure in $Hg2$. Measurements have also been obtained with a $\mathrm{<mrow\; data-mjx-texclass="ORD">200</mrow>}$Hg cell and with a high power Xe are lamp source. Possible interpretation of the observed spectra will be discussed.