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Title: Activity measurement of Fe 60 through the decay of Co 60 m and confirmation of its half-life

Abstract

The half-life of the neutron-rich nuclide, 60Fe has been in dispute in recent years. A measurement in 2009 published a value of (2.62 ± 0.04) × 106 years, almost twice that of the previously accepted value from 1984 of (1.49 ± 0.27) × 106 years. This longer half-life was confirmed in 2015 by a second measurement, resulting in a value of (2.50 ± 0.12) × 106 years. All three half-life measurements used the grow-in of the γ-ray lines in 60Ni from the decay of the ground state of 60Co (t1/2=5.27 years) to determine the activity of a sample with a known number of 60Fe atoms. In contrast, the work presented here measured the 60Fe activity directly via the 58.6 keV γ-ray line from the short-lived isomeric state of 60Co (t1/2=10.5 minutes), thus being independent of any possible contamination from long-lived 60gCo. A fraction of the material from the 2015 experiment with a known number of 60Fe atoms was used for the activity measurement, resulting in a half-life value of (2.72 ± 0.16) × 106 years, confirming again the longer half-life. In addition, 60Fe/56Fe isotopic ratios of samples with two different dilutions of this material were measured with Accelerator Mass Spectrometrymore » (AMS) to determine the number of 60Fe atoms. Combining this with our activity measurement resulted in a half-life value of (2.69 ± 0.28) × 106 years, again agreeing with the longer half-life.« less

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
National Science Foundation (NSF)
OSTI Identifier:
1462715
DOE Contract Number:  
AC02-06CH11357
Resource Type:
Journal Article
Journal Name:
Physical Review C
Additional Journal Information:
Journal Volume: 95; Journal Issue: 5; Journal ID: ISSN 2469-9985
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English

Citation Formats

Ostdiek, Karen M., Anderson, Tyler S., Bauder, William K., Bowers, Matthew R., Clark, Adam M., Collon, Philippe, Lu, Wenting, Nelson, Austin D., Robertson, Daniel, Skulski, Michael, Dressler, Rugard, Schumann, Dorothea, Greene, John P., Kutschera, Walter, and Paul, Michael. Activity measurement of Fe60 through the decay of Co60m and confirmation of its half-life. United States: N. p., 2017. Web. doi:10.1103/PhysRevC.95.055809.
Ostdiek, Karen M., Anderson, Tyler S., Bauder, William K., Bowers, Matthew R., Clark, Adam M., Collon, Philippe, Lu, Wenting, Nelson, Austin D., Robertson, Daniel, Skulski, Michael, Dressler, Rugard, Schumann, Dorothea, Greene, John P., Kutschera, Walter, & Paul, Michael. Activity measurement of Fe60 through the decay of Co60m and confirmation of its half-life. United States. doi:10.1103/PhysRevC.95.055809.
Ostdiek, Karen M., Anderson, Tyler S., Bauder, William K., Bowers, Matthew R., Clark, Adam M., Collon, Philippe, Lu, Wenting, Nelson, Austin D., Robertson, Daniel, Skulski, Michael, Dressler, Rugard, Schumann, Dorothea, Greene, John P., Kutschera, Walter, and Paul, Michael. Mon . "Activity measurement of Fe60 through the decay of Co60m and confirmation of its half-life". United States. doi:10.1103/PhysRevC.95.055809.
@article{osti_1462715,
title = {Activity measurement of Fe60 through the decay of Co60m and confirmation of its half-life},
author = {Ostdiek, Karen M. and Anderson, Tyler S. and Bauder, William K. and Bowers, Matthew R. and Clark, Adam M. and Collon, Philippe and Lu, Wenting and Nelson, Austin D. and Robertson, Daniel and Skulski, Michael and Dressler, Rugard and Schumann, Dorothea and Greene, John P. and Kutschera, Walter and Paul, Michael},
abstractNote = {The half-life of the neutron-rich nuclide, 60Fe has been in dispute in recent years. A measurement in 2009 published a value of (2.62 ± 0.04) × 106 years, almost twice that of the previously accepted value from 1984 of (1.49 ± 0.27) × 106 years. This longer half-life was confirmed in 2015 by a second measurement, resulting in a value of (2.50 ± 0.12) × 106 years. All three half-life measurements used the grow-in of the γ-ray lines in 60Ni from the decay of the ground state of 60Co (t1/2=5.27 years) to determine the activity of a sample with a known number of 60Fe atoms. In contrast, the work presented here measured the 60Fe activity directly via the 58.6 keV γ-ray line from the short-lived isomeric state of 60Co (t1/2=10.5 minutes), thus being independent of any possible contamination from long-lived 60gCo. A fraction of the material from the 2015 experiment with a known number of 60Fe atoms was used for the activity measurement, resulting in a half-life value of (2.72 ± 0.16) × 106 years, confirming again the longer half-life. In addition, 60Fe/56Fe isotopic ratios of samples with two different dilutions of this material were measured with Accelerator Mass Spectrometry (AMS) to determine the number of 60Fe atoms. Combining this with our activity measurement resulted in a half-life value of (2.69 ± 0.28) × 106 years, again agreeing with the longer half-life.},
doi = {10.1103/PhysRevC.95.055809},
journal = {Physical Review C},
issn = {2469-9985},
number = 5,
volume = 95,
place = {United States},
year = {2017},
month = {5}
}

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