The effect of electron scavengers on the γ-radiolysis of gaseous H₂S

Abstract

Recent publications ( 1 4 ) have dealt with the effect of electron scavengers on the radiolysis of simple inorganic gaseous hydrides. We would like to present some results of a preliminary study on the radiolysis of gaseous H2S that are, in general, quite different from those above (14).Matheson C.P. grade H,S (99.7 %) was found to contain CO, (-0.2 %) and CS, (< 0.001 %) as impurities when checked by gas chromatography. A 3 m Poropaq Q column maintained at 65 "C, helium carrier gas, and thermal conductivity detection were used (5). After several freezepump-thaw cycles at -130 "C, the concentration of CO, was reduced to -0.005 %. Some of this H,S was irradiated to a dose of about 4 x lo2, eV g-l. After degassing at -196 "C, this H,S was found to contain -0.005 % CO, and no detectable amount of CS,. Radiolysis experiments with the pre-irradiated H,S gave identical results to the untreated H,S, and so the latter was used for the bulk of the work presented here. SF, and N,O (Matheson) were degassed several times by freeze-pump-thaw cycles at liquid nitrogen temperature and were used without further purification.Dosimetry was effected by ion current measurements in vessels similar to those described by Back et al. (6), the extrapolation method of Scott and Greening (7) being used to obtain saturation ion currents. The same vessels were also used as irradiation vessels, as were ordinary Pyrex vessels of similar geometry. All vessels were baked out at 400 "C, to a pressure of less than lo-' Torr prior to filling and irradiating.

Radiolysis of Hydrogen Sulfide at Very High Dose Rates. The Effect of SF61

“…As discussed in the previous section, the fair agreement between the low dose rate yield of G(H,) = 7.0-7.9 (7,9,10) and the limiting yield of G(H,) = 7.9 + 0.3 with SF, at high dose rates suggests that there is no contribution from neutralization at low dose rates. This is confirmed by the absence of an effect of SF, and N 2 0 on G(H2) at low dose rates (1,7,9,10) and it is further confirmed by the limiting yield in multipulse irradiations at high dose rates where G(H,) x 8, and is unaffected by SF,, Figs. 3A and 3B.…”

“…They also reported that this yield is reduced by the addition of SF,, although they did not state by how much. Huyton and Woodward (7,8) y-irradiated gaseous H2S and measured the dose by ion chamber measurements. They report G(H2) = 7.0 _+ 0.2 at 800 Torr and that neither N 2 0 nor SF, has any effect on this yield (7).…”

“…Huyton and Woodward (7,8) y-irradiated gaseous H2S and measured the dose by ion chamber measurements. They report G(H2) = 7.0 _+ 0.2 at 800 Torr and that neither N 2 0 nor SF, has any effect on this yield (7). 'AECL No.…”

“…It appears then that the effect of dose rate on the H2 yield is due to a change in the ionic reactions and this is supported by the change in behavior with electron scavengers. Huyton and Woodward (7) suggested from their low dose rate work that the neutralization process in H2S-SF, mixtures is [l 1. ] giving the same H atom yield as in pure H2S where they suggested the neutralization process is [12] 1121 H3S+ + X -+ H + H 2 S + X where Xmay be H2S-or some other negative species.…”