HALF-LIVES OF TI-44 AND BI-207

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 Ti44 and one of Bi207. Comparison counts were taken on a Cl36 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 Bi207 source and on one of the Ti44 sources, and 1 year on the second Ti44 sample, half-lives were obtained as follows: Ti44, 66.6(16) yr and Bi207, 34.9(4) yr. The Bi207 value lies between the two most recently reported values. In the case of Ti44 there are discrepancies with all three previous results including an Argonne accelerator mass spectroscopy value of 54.2(21) yr. © 1990 The American Physical Society.