Knowledge Bank

The (1) $b3\Pi u$ state of $Li2$ has been investigated by using two different optical-optical double resonance mechanisms with single mode dye lasers. 1) Perturbation facilitated optical-optical double resonance Using established ""gateways"" to the triplet manifold in $\mathrm{<mrow\; data-mjx-texclass="ORD">7</mrow>}Li2$ [1], it is possible to reach many vibrational levels of the (2) $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi g$ and (1) $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Delta g$ Rydberg states with R6G plus DCM or LD700 dyes. The range of $N\prime$ is very limeted because of the restricted access to the triplet systems. Direct fluorescence from these levels very limited because of the restricted access to the triplet systems. Direct fluorescence from these levels to vibrational levels $1\le v\prime \prime \le 27$ in the $b3\Pi u$ state were recorded at 0.07 cm $\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ resolution on a Fourier transform spectrometer. 2) Optical-optical double resonance within the singlet manifold, followed by collisionally induced fluorescence. When levels v=2 and 3 of the F $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma g+$ state were excited, collisional processes resulted in efficient energy transfer to the (1) $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Delta g$ state. Rotational levels $N\prime \le 20$ were observed in the levels $v\prime =0,1$ and 2 of (1) $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Delta g$. Bands of the (1) $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Delta g\to (1)b3\Pi u$ system with $0\le v\prime \prime \le 7$ were recorded on the Fourier transform spectrometer at a resolution of 0.07 cm $\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$. Their structure clearly reveals the effects of interaction between the $b3\Pi u$ state and the repulsive inner wall of the $a3\Sigma u+$ state, as alternate rotational levels are shifted and broadened by predissociation. Combining the data from both experiments, we have derived an RKR curve for the $b3\Pi u$ state up to v=27 (which covers about 65% of the total well depth), and have studied the shifts caused by predissociation as a function of v"" and N"". These are compared with those observed in the past for the $\mathrm{<mrow\; data-mjx-texclass="ORD">6</mrow>}Li2$ molecule [2], and the results will be discussed.