Improved measurement of the half-life of the Jπ=8- nuclear isomer Eu 152m2

P. Humby, A. Simon, C. W. Beausang, T. J. Ross, R. O. Hughes, J. T. Burke, R. J. Casperson, J. Koglin, S. Ota, J. M. Allmond, M. McCleskey, E. McCleskey, A. Saastamoinen, R. Chyzh, M. Dag, K. Gell, T. Tarlow, G. Vyas

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Abstract

The standard γ-ray energy calibration source Eu152 is well known based on the 13.5 y decay of its ground state. However, in addition to this decay Eu152 also has two relatively long-lived isomeric states: a 9 h Jπ=0- state at E∗=46 keV and a 96 min Jπ=8- state at E∗=148 keV. Here we report a new measurement of the half-lives of both of these isomeric states. Excited states in Eu152 were populated following the Sm154(p,3n) reaction using a 25 MeV proton beam from the K-150 cyclotron at the Cyclotron Institute of Texas A&M University. Post irradiation, γ rays from the de-excitation of the long lived isomeric states were measured using the six BGO shielded high-purity germanium (HPGe) clover detectors that are part of the STARLiTeR array. The half-life of the Jπ=8- isomer Eu152m2 was obtained by measuring the decrease in intensity of the 90 keV γ ray from the cascade to the ground state. The half-life of this state was measured to be 95.8(4) min which is in agreement with and significantly more precise than the previously measured value of 96(1) min. In a manner similar to the ground state the second long-lived isomer Eu151m1, the Jπ=0- state at 46 keV, β decays to excited states in Gd152 and Sm152. The half-life of this state was measured to be 9.39(7) h using five γ-ray transitions.

Original languageEnglish
Article number024322
JournalPhysical Review C - Nuclear Physics
Volume91
Issue number2
DOIs
StatePublished - Feb 23 2015

Funding

FundersFunder number
National Science Foundation

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