Knowledge Bank

The first observation of 2 $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi u-X1\Sigma g+$ transitions is reported. Rotationally resolved transitions of the 2 $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi u(1u)X1\Sigma g+(0g+)$ and 2 $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi u(0u+)-X1\Sigma g+(0g+)$ are observed by resonance enhanced 2-photon ionization (RE2PI) method in a pulsed molecular beam. $\Omega$-doubling and interference induced rotational branch intensity anomalies are observed for 2 $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi u(1u)-X1\Sigma g+(0g+)$ transitions. Both of 2 $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi u(0u+)$ and 2 $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi u(1u)$ states are strongly mixed with singlet slates by spin-orbit coupling. The former with 2 $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma u+$ and the latter with 2 $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Pi u$. In relatively weak 2 $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi u(1u)$ bands P-branch rotational lines disappear and the intensities of R-branch rotational lines are enhanced. These intensity anomalies in 2 $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi u(1u)-X1\Sigma g+(0g+)$ transition, due to an interference effect between parallel and perpendicular transition amplitudes, is caused by $\Delta \Omega =\pm 1$ perturbation. The molecular constants of 2 $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi u(0u+)-X1\Sigma g+(0g+)$ transition are determined as $Tc=19784.2588\pm 0.0088cm-1,\omega e=42.1954\pm 0.0060cm-1,\omega exe=0.1701\pm 0.0011cm-1,\omega eye=-0.001096\pm 0.000057cm-1,Be=0.018603\pm 0.000018cm-1$ for $\mathrm{<mrow\; data-mjx-texclass="ORD">8</mrow>}5Rb2$. The spin-orbit coupling constant A and $\Omega$-doubling parameters p and q are determined by simultaneous fitting of the rotational contours of both 2 $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi u(1u)-X1(\Sigma g+)$ and 2 $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi u(0u+)-X1\Sigma g+(0g+)$ transitions.