Energy partition in the γ-radiolysis of gaseous H2S + N2, H2S + Ar and H2S + Xe mixtures

Abstract

Ionization measurements in H2+ N2, H2S + Ar, and H2S + Xe mixtures are used to determine apparent stopping power ratios for the mixtures, or “energy partition parameters”. The values found for H2S + N2, H2S + Ar, and H2S + Xe are 0.20, 0.95, and 3.60 respectively, as compared to the calculated values of 0.82, 0.95, and 2.46. In H2S + Ar mixtures a “Jesse effect” is observed that increases the ion yield by 2 units, this effect being quenched out between stopping power fractions Z= 0.2–0.4. Measurement of sulphur yields in H2S + N2 mixtures enables an energy partition parameter of 0.5 to be evaluated. The difference from the value obtained by ionization measurements being explained by a small “Jesse effect”. In H2S + Ar mixtures the sulphur yield G(S) was always > G(S)= 7.0 found in pure H2S and approached values as high as 24. The sulphur yield also increased between Z= 0.2 and 0.4 by twice the decrease in the ion yield. G(S) in H2S + Xe mixtures never rises above 7.0, and the values can be justified by energy transfer from Xe*(G≃ 5.0) to H2S to give H2+ S*, where S* is not a ground state S(3P) atom. No such simple mechanism will explain the results in H2S + Ar mixtures. Butadiene was used as an SH and S(3P) scavenger, and the ratio of scavengeable to non-scavengeable sulphur in H2+ Ar mixtures is similar to that in H2S i.e. ∼13. In H2S + Xe mixtures this ratio is ∼3–4, and is explained by production of excited S atoms (S*), which react with H2S to give H2 and S2.