High resolution laser spectroscopy of spatially restricted hot alkali atomic and dimer vapor

In this paper we discuss a novel use of a Cs-filled optical cell with micrometric thickness. The cell intrinsically contains an extremely small number of Rb atoms. When heated up to temperatures around 350 $$^\circ $$C, the vapor in the cell consists of: (i) Cs atoms, (ii) an order of magnitude lower concentration $$\hbox {Cs}_2$$ dimers and (iii) a small number of Rb atoms. This mixture is a high density but optically thin alkali vapor layer, and the produced complex ensemble of $$\hbox {Cs}_2$$ diatomic molecules, together with Rubidium and Cesium atoms can be investigated by means of linear/nonlinear spectroscopy. In this work we study the fluorescence and selective reflection spectral profiles of Rb atoms in the presence of high-density Cs atoms considered as a buffer gas for the Rb atoms and Cs dimers. In addition, the Rb hyperfine transition spectrum is used as a precise frequency reference for the measurement of the spectral profile widths and the frequency positions of the experimentally registered spectral lines of $$\hbox {Cs}_2$$ molecules in the spectral region around the Rb $$\hbox {D}_2$$ resonance line.