Ionization by Alpha Particles in Binary Gas Mixtures

Abstract

825are somewhat greater than those estimated from 20" acidity data; however, this is the direction expected, and of the approximate magnitude predicted, from studies of the temperature coefficient of U(V1) hydrolysis in nitrate medium.*aThe question of the importance of other species which may be present in minor amounts is no more resolved by the present results than by the earlier study. For example, it was apparent that about as satisfactory an interpretation could be obtained with a scheme including UOzOH+, although there would be considerable uncertainty in the values of el,l. Similarly, our conclusions for the perchlorate solutions agree in general with those of SuttonJ6 though he includes a small contribution of the (3,4) species.The most important point of disagreement with the interpretation of acidity measurements on a core-link modelll seems to be resolved, since the St>ockholm group now postulate an important contribution by the (3,5) species, which is not of the core-link type.l2 They still postulate the presence of several higher corelink species, for which we do not find any evidence in our results, but since the constants quoted for these species are rather low, the remaining disagreement is perhaps more in a conceptual model of hydrolysis rather than in a practical description of U(V1) solution chemistry. From a recent publication,13 it appears that even this disagreement may no longer exist.Acknowledgment.-We wish to express indebtedness to Kurt A. Kraus for many helpful and stimulating discussions and to Neva Harrison for technical assistance.The W value (average energy loss per ion pair) for a-particles has been measured in a number of binary gas mixtures of molecular gases as a function of the fract'ional pressures. The W of the mixture ( Wij) can be represented in terms of the 14"s of the pure constituent gases Wi, Wj) and the fractional pressures ( P i , Pj) by the relation:, in whichfij is a constant determined empirically for each pair of gases. These constants verynearly satisfy the relationshipfij = fj/fi = (fj/fk)/(fi/jk) = jkj/jki,where i, j, and k refer to any three gases. Thus, if the followingj-values are assigned to the gases in this study (Nz, 1;COz, 1.8; H,, 0.5; 02, 1.3; CH,, 1.8; CeH4, 3.4; GH6, 3.5; CJ&, 4.5; C,Hs, 4.5; C9H8, 6.3) then the constant f i j determined from the ratio of any two of these will serve to predict the W of any mixture of these two gases with an accuracy better than 1%. Slight departures from the W predicted by the above equation have been noted in the case of nitrogen mixtures, indicative of an effect similar to t'hat observed in the noble gases when small amounts of impurities are added.

Energy dependence of W for alpha particles in N2, CO2, CH4, Ar, H2 and Rossi-type tissue-equivalent gases

“…Thus, for uniform weighting with respect to v (i.e. no change in W with energy) the mean energy of alphas for a particular measurement will be given by W for TE gas was measured and also determined from measurements of W for the constituent gases (nitrogen, carbon dioxide and methane) by using the following expressions (Strickler 1963) :…”

Absolute W value measurements for 5.9 keV x rays in Ne–Xe mixtures at atmospheric pressures

“…[10][11][12][13][14][15] To study the ionization yield in a mixture these treatments start from the assumption that each gas compo-nent receives a fraction of the incident energy, determined by a dimensionless constant z. [10][11][12][13][14][15] To study the ionization yield in a mixture these treatments start from the assumption that each gas compo-nent receives a fraction of the incident energy, determined by a dimensionless constant z.…”

Electron degradation and yields of initial products: The Fano factor for mixtures of argon and molecular hydrogen

“…One reason for the choice is that electron collision cross sections for each component are well established. Another reason is that this mixture is "regular" in the sense [6] that there is no appreciable intermolecular energy transfer between the two constituents; hence the results thus obtained should be comparable to measurements that pertain to the time much later than the completion of electron degradation. Then it follows that where o. , represents the total ionization cross section.…”