Knowledge Bank

We have performed a series of optical-optical double resonance experiments with one or two cw Ti:sapphire lasers, to excite the 2~$\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Pi g$ state of Rb$2$, recording infrared fluorescence from 2~$\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Pi g$ on a Fourier transform spectrometer. Fluorescence from the lower vibrational levels of 2~$\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Pi g$ (T = 22069.56 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$) is dominated by transitions to the B $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Pi u$ state studied by Amiot and Verges, Chem. Phys. Lett. 294, 91-98 (1997). Vibrational and rotational relaxation from laser-pumped levels v' 15 now give a rather complete description around the potential minimum of the 2~$\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Pi g$ state, completing the observations for 6 $\le$~v~$\le$ 50 reported by Han et al, Chem. Phys. Lett. 538, 1-4 (2011) last year. Fluorescence from v' $>$ 35, occurs also to the 0$+$ components of the A~$^{1}\Sigma_u^+ \sim $b$~^{3}\Pi_u $ complex. Fitting all available 2~$^{1}\Pi_g \rightarrow $B$^{1}\Pi_u $ data for $\mathrm{<mrow\; data-mjx-texclass="ORD">85</mrow>}$Rb$2$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">85</mrow>}$Rb$\mathrm{<mrow\; data-mjx-texclass="ORD">87</mrow>}$Rb (several thousand transitions) has also given an improved description of the bottom of the B $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Pi u$ state potential well. The 2~$\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Pi g$ state correlates at long-range with Rb 5s + Rb 4d $2D3/2$ atoms (A.-R. Allouche, M. Aubert-Frecon, J. Chem Phys 136, 37-41 (2012)), giving a dissociation energy of 1279.6 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$. Most new data lie below v = 45, 250 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ below this dissociation threshold.