“…Isotopes 197,198,199,and 200 have been assigned half-lives of 2.7, 5.3, 7.2, and 27 hr, respectively, and decay principally by electron capture. Tl 204 decays by beta emission with a half-life of approximately 4.1 yr. [12][13][14][15][16] Isotope identification for the neutrondeficient isotopes consists of observing the decay of a sample collected at the appropriate spin position. Tl 204 is, by arguments previously given, pure by activity when run.…”