The Half-lives of ${}^{132}$La and ${}^{135}$La

Abstract

The half-lives of ${}^{135}$La and ${}^{132}$La were determined via gamma spectroscopy and high-precision ionization chamber measurements. The results are 18.930(6) h for ${}^{135}$La and 4.59(4) h for ${}^{132}$La compared to the previously compiled values of 19.5(2) h and 4.8(2) h, respectively. The new results represent an improvement in the precision and accuracy of both values. These lanthanum isotopes comprise a medically interesting system with positron emitter ${}^{132}$La and Auger electron emitter ${}^{135}$La forming a matched pair for internal diagnostics and therapeutics. The precise half-lives are necessary for proper evaluation of their value in medicine and for a more representative tabulation of nuclear data.

11 pages, 3 figures