Half-lives ofTi44andBi207

An end-window gas-flow proportional counter system, including an automatic precision sample changer, was used to measure the decay of radiations from two samples of ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ti}$ and one of ${}_{}{}^{207}{}_{}{}^{}\mathrm{Bi}$. Comparison counts were taken on a ${}_{}{}^{36}{}_{}{}^{}\mathrm{Cl}$ standard, and the ratio of counts determined the decay. Points consisted of alternate 30-min counts on each sample and on the standard, totaling 30 h on each, and were taken at intervals of about one month. Based on 3 years of counting on the ${}_{}{}^{207}{}_{}{}^{}\mathrm{Bi}$ source and on one of the ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ti}$ sources, and 1 year on the second ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ti}$ sample, half-lives were obtained as follows: ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ti}$, 66.6(16) yr and ${}_{}{}^{207}{}_{}{}^{}\mathrm{Bi}$, 34.9(4) yr. The ${}_{}{}^{207}{}_{}{}^{}\mathrm{Bi}$ value lies between the two most recently reported values. In the case of ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ti}$ there are discrepancies with all three previous results including an Argonne accelerator mass spectroscopy value of 54.2(21) yr.