Activity measurement of Fe60 through the decay of Co60m and confirmation of its half-life
| Autor: | Karen Ostdiek, Austin Nelson, John P. Greene, Michael Skulski, Walter Kutschera, A. M. Clark, Philippe Collon, Rugard Dressler, Matthew Bowers, Tyler Anderson, Michael Paul, W. Bauder, Daniel Robertson, Dorothea Schumann, Wenting Lu |
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| Rok vydání: | 2017 |
| Předmět: | |
| Zdroj: | Physical Review C. 95 |
| ISSN: | 2469-9993 2469-9985 |
| DOI: | 10.1103/physrevc.95.055809 |
| Popis: | The half-life of the neutron-rich nuclide $^{60}\mathrm{Fe}$ has been in dispute in recent years. A measurement in 2009 published a value of $(2.62\ifmmode\pm\else\textpm\fi{}0.04)\ifmmode\times\else\texttimes\fi{}{10}^{6}$ years, almost twice that of the previously accepted value from 1984 of $(1.49\ifmmode\pm\else\textpm\fi{}0.27)\ifmmode\times\else\texttimes\fi{}{10}^{6}$ yr. This longer half-life was confirmed in 2015 by a second measurement, resulting in a value of $(2.50\ifmmode\pm\else\textpm\fi{}0.12)\ifmmode\times\else\texttimes\fi{}{10}^{6}$ yr. All three half-life measurements used the grow-in of the $\ensuremath{\gamma}$-ray lines in $^{60}\mathrm{Ni}$ from the decay of the ground state of $^{60}\mathrm{Co}$ (${t}_{1/2}=5.27$ yr) to determine the activity of a sample with a known number of $^{60}\mathrm{Fe}$ atoms. In contrast, the work presented here measured the $^{60}\mathrm{Fe}$ activity directly via the 58.6 keV $\ensuremath{\gamma}$-ray line from the short-lived isomeric state of $^{60}\mathrm{Co}$ (${t}_{1/2}=10.5$ min), thus being independent of any possible contamination from long-lived $^{60\mathrm{g}}\mathrm{Co}$. A fraction of the material from the 2015 experiment with a known number of $^{60}\mathrm{Fe}$ atoms was used for the activity measurement, resulting in a half-life value of $(2.72\ifmmode\pm\else\textpm\fi{}0.16)\ifmmode\times\else\texttimes\fi{}{10}^{6}$ yr, confirming again the longer half-life. In addition, $^{60}\mathrm{Fe}/^{56}\mathrm{Fe}$ isotopic ratios of samples with two different dilutions of this material were measured with accelerator mass spectrometry to determine the number of $^{60}\mathrm{Fe}$ atoms. Combining this with our activity measurement resulted in a half-life value of $(2.69\ifmmode\pm\else\textpm\fi{}0.28)\ifmmode\times\else\texttimes\fi{}{10}^{6}$ yr, again agreeing with the longer half-life. |
| Databáze: | OpenAIRE |
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