Resonant laser-induced formation of caesium hydride molecules in a room temperature vapour cell: experimental results and rate equation calculations

Abstract

Photochemical formation of caesium hydride in a room temperature cell containing Cs vapour and H2 under illumination of the mixture by laser radiation tuned to the D2 atomic resonance line of Cs is reported. The chemical reaction is accompanied by dramatic changes in magnitude of the resonant absorption and fluorescence of Cs atoms in H2 environment as compared with a pure Cs vapour case. A theoretical model, which takes into account all the optical and chemical processes involved at these densities, is developed. The effective rate of a two-step chemical reaction (1 ± 0.3) × 10−10 cm3 s−1 is determined from the fitting of experimental results to this model, exploiting the laser intensity dependence of the fluorescence signal. Continuous (several hours) illumination of the cell by radiation tuned to the Cs D2 line results in decrease of the hydrogen pressure in the cell, which is an additional proof for the formation of CsH molecules. The proposed investigation technique is applicable for a large variety of resonant photochemical reactions. Possible application for isotope separation is discussed.