Alpha-decay from the 3.5 eV isomer of 229Th

T. Mitsugashira, M. Hara, T. Ohtsuki, H. Yuki, K. Takamiya, Y. Kasamatsu, A. Shinohara, H. Kikunaga, T. Nakanishi

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20 Citations (Scopus)


The alpha-decay of a low energy isomer of 229Th at about 3.5 eV was sought by producing it through the (γ,n) reaction on a 230Th target. Thorium isotopes in the reaction products were isolated and purified by anion exchange chromatography in a concentrated nitric acid medium to remove lanthanides fission products. The thorium fraction was further purified by samarium fluoride coprecipitation and the precipitate was mounted as a source for α-spectroscopy. Decaying α-signals were observed in the energy region that was expected for 229mTh, i.e., between 4.83 and 5.08 MeV. The half-life of the decaying component was determined from repeated experiments to be 13.9±3 hours.

Original languageEnglish
Pages (from-to)63-66
Number of pages4
JournalJournal of Radioanalytical and Nuclear Chemistry
Issue number1
Publication statusPublished - 2003 Jan 1


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