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

Abstract

The radiation of a multimode tunable laser photoexcites cesium atoms from the ground state to the 7 P_1/2 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.