Absolute Rate of the Reaction H+H2S

Flash photolysis coupled with resonance fluorescence of Lyman‐α radiation at 121.6 nm has been used to investigate the rate of reaction of H atoms with H₂S over the temperature range 190–464°K. Conditions were chosen under which atom–radical and radical–radical reactions were unimportant and only the H‐atom–H₂S reaction occurred. The rate constant thus obtained can be expressed as $k_1{\text{\hspace{0.17em}=\hspace{0.17em}(1.29\hspace{0.17em}±\hspace{0.17em}0.15)\hspace{0.17em}×\hspace{0.17em}10}}^{\text{−11}}\exp \text{[−\hspace{0.17em}(1709\hspace{0.17em}±\hspace{0.17em}60)\hspace{0.17em}/\hspace{0.17em}1.987T]}{\mathrm{cm}}^3{\mathrm{molecule}}^{\text{−1}}·{\sec }^{\text{−1}}$ . Comparison of the Arrhenius $A$ factor with that predicted by entropy considerations suggests a somewhat loose activated complex, but not as loose as expected on the basis of the exothermicity of the H+H₂S reaction.