Charge Spectrometry forXe133-Cs133

Abstract

The distribution in charge of the product atoms of the radioactive decay ${\mathrm{Xe}}^{133}$-${\mathrm{Cs}}^{133}$ has been examined under magnetic analysis. The relative intensities are found to be as follows, expressed in percent of the decay events, and going respectively from charge 1 through charge 23: 34.1, 3.74, 2.27, 2.15, 2.99, 4.27, 6.14, 9.5, 12.3, 9.0, 6.06, 3.32, 1.76, 1.06, 0.66, 0.32, 0.13, 0.050, 0.014, 0.0075, 0.0027, 0.0013, 0.0005. In interpreting this charge spectrum, the initial part (charges 1 through 4) is attributed mainly to atoms that escape internal conversion, and the subsequent rise to a maximum at charge 9 and decrease to charge 23 is attributed to atoms that suffer internal conversion. The ratio of the intensities of the two parts of the distribution gives a total internal conversion coefficient for the $K$, $L$, and $M$ shells of 1.4, in rough agreement with work of others. Comparison is made with the charge spectrum arising from internal conversion in ${\mathrm{Xe}}^{131m}$-${\mathrm{Xe}}^{131}$, which had previously been measured in the same apparatus. From the low-charge end of the spectrum, the probabilities of electron loss as a result of the beta decay alone are derived as follows: no-electron loss, 0.8; 1-electron loss, 0.08; 2-electron loss, 0.04; 3-electron loss, 0.03. The high-charge side of the spectrum shows a shallow dip in the region of charges 12, 13 and 14, and beyond that point there is relatively more intensity in ${\mathrm{Xe}}^{133}$-${\mathrm{Cs}}^{133}$ than there is in ${\mathrm{Xe}}^{131m}$-${\mathrm{Xe}}^{131}$. The difference in shape probably results both from the higher $\frac{K}{\mathrm{}(L+M)\mathrm{}}$ conversion ratio of ${\mathrm{Xe}}^{133}$-${\mathrm{Cs}}^{133}$ as compared with ${\mathrm{Xe}}^{131m}$-${\mathrm{Xe}}^{131}$, and from the fact that the beta emission in ${\mathrm{Xe}}^{133}$-${\mathrm{Cs}}^{133}$ introduces electron loss by shake-off. The dip at charges 12, 13, and 14 suggests an underlying structure in the total distribution, comprising subspectra associated with the individual electron shells in which the vacancy cascades originate.