Effect of radical scavengers and electric fields on the γ-radiolysis of gaseous hydrogen sulphide

Abstract

In they-radiolysis of H2S with added buta-1,3-diene, H atoms appear to react before they become thermalised. With added benzene, propene, and but-1-ene insufficient scavenging occurs to say with certainty whether a similar situation applies, but indications are that it may be so for propene, and but-1-ene. Investigation of the effect of but-1-ene on the sulphur yield, indicates a dose rate effect which is explained by a competition between ion-recombination and diffusion to the wall enhanced by convection currents. Yields of G(H2) = G(S) = 0.5 unscavengable by buta-1,3-diene are indicated, and evidence is given that excited sulphur atoms (S*) and S+ ions are probable precursors of these yields. Nitric oxide appears to react with SH radicals in a chain process producing H20, N20 and S. Electric fields do not affect the radiation yields until electron acceleration just before saturation occurs, causes increased decomposition. The ratio of sulphur scavengable in the presence of a field is -4 : 1, which is much lower than in the absence of a field (13 : 1). This is evidence for production of excited S atoms by field accelerated electrons.

Rare gas sensitized radiolysis of hydrogen sulfide in the presence of butadiene

“…The experiments were reportedly hampered by heterogeneous processes. On the other hand, the rate constant for (2) given in ref 6 is in good agreement with the other values mentioned above. If one would accept both values to be truly homogeneous gas phase values, one is left with explaining an enormously large isotope effect.…”

“…In conclusion, it may be stated that (1) atomic hydrogen in both H2S-C4H6-Xe and H2S-C4H6-Kr mixtures is produced mainly by excitation transfer from a rare gas atom to the hydrogen sulfide molecule and to a minor extent by direct radiolysis of hydrogen sulfide (but on this problem see the last part of this paper), (2) excitation transfer to hydrogen sulfide is competing with that to butadiene. The experimental yield of hydrogen, G(H2)*, results from this competition and from the competition between reactions 1 and 2.…”

“…It has been stated that addition of butadiene causes a slow decrease in G(H2) and drastically reduces G(S) by G ^6 in the y radiolysis of hydrogen sulfide. The rate constant ratio ^h+Hís/^h+ca was reported to be twice as great as that for thermal hydrogen atoms (0.26 in ref 2 and 0.20 in ref 3). However, the data for the rare gas sensitized radiolysis4 included only G(S) and were obtained mainly at high concentrations of hydrogen sulfide in mixtures (more than 20 mol %) thus involving a large part of the primary -radiolysis effect. In this contribution we present detailed results on the influence of butadiene on both hydrogen and sulfur yields at small concentrations (below 10 mol %) of hydrogen sulfide in argon, krypton, and xenon.…”