Knowledge Bank

Previous studies of the excited electronic states of $Li2$ in the visible and UV regions1 has recently been extended into the infra-red. The $11\Pi g$ state has been observed by pulsed optical optical double resonance of the metal vapor in a heat-pipe oven. Following excitation to selected levels of the $A11\Sigma u\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ state, the 2nd Stokes output of a hydrogen Raman shifter is directed into the oven. Transitions from $A1\Sigma u\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ state levels to the $11\Pi g$ state are detected by monitoring blue-green fluorescence as the Raman shifted light is scanned through the range, $1.1\mu m-1.3\mu m$. The observations include 33 vibrational levels excited from $v=0$ in the A state. Molecular constants and a potential curve for the $11\Pi g$ will be reported. Together with the recent FT-1R work of B. Barakat et al. 2, this study completes the observation of all singlet states arising from the Li(2s) + Li(2p) dissociation limit.