Kinetics of the thermal decomposition of H2Se

We have found that H2Se decomposes by a homogeneous gas-phase reaction between 673 and 748 K and 70 and 630 Torr. The reaction reaches equilibrium in approximately 200 min at 673 K and 5 min at 748 K, with ∼65% of the H2Se decomposed. The reaction order is near unity at 630 Torr but gradually increases with decreasing pressure. We have measured an activation energy of 46.4 ± 0.1 kcal/mol and an A-factor of 3.8 × 1010 in the first-order region.