Mechanism of S2 chemiluminescence in the reaction of hydrogen atoms with hydrogen sulphide

Ground-state sulphur atoms were generated in a discharge flow system by the rapid reaction between H and H2S: H + H2S = H2+ HS (1), H + HS = H2+ S (2) The resulting chemiluminescence by the B3Σ–u state of S2 is shown to arise (a) by two-body combination of S atoms into level v′= 10; (b) by three-body recombination into lower levels: S(3P)+ S(3P)+ M = S*2(B3Σ–uv′⩽9)+ M (3), S*2= S2(X3Σ–g)+hv(4), S*2+ M = S2+ M (5) with k3=(1.0 ± 0.2)× 1015 cm6 mole–2 sec–1 and k4/k5= 2.0 × 10–7 mole cm–3 for M = Ar at 298°K; also D(S—S)= 101.7 ± 0.4 kcal/mole. The mechanism of the sulphur-catalyzed heterogeneous recombination of hydrogen atoms is studied and discussed.