Experimental investigation of cesium hydride formation by reactive interaction between Cs(7 P) and H2 molecules

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Abstract
The radiation of a multimode tunable laser photoexcites cesium atoms from the ground state to the 7 P1/2 level in a mixture of cesium vapor and hydrogen. Cesium hydride is formed by the Cs(7 P)+H2 reaction and observed by laser fluorescence. The relation between the concentration of CsH and those of other species present in the medium [Cs(7 P),H2, and Cs(6 S)] is studied in both a stationary and a transient laser irradiation regime. The rate of CsH formation is found to be proportional not only to [Cs(7 P)] and [H2] but also to [Cs(6 S)]. This observation suggests that, under our experimental conditions {[Cs] = (0.5–8)×1016 cm−3,[H2] = (8–80)×1016 cm−3}, CsH molecules are not created by a direct interaction between Cs(7 P) and H2 but most probably through a two‐step reaction. This process might involve intermediate species such as vibrationally excited H2 molecules. An absolute value of the rate coefficient k = {[Cs(7 P)][H2][Cs]}−1d[CsH]/dt?5×10−31 cm6 s−1 is estimated.