Precise life-time measurements of unstable nuclides in capsulated in fullerene cage

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A precise measurement of decay constant for ^7Be encapsulated in fullerene cage were performed with extreme conditions, such as 6K temperature. The results measured in 6K were compared with data for the normal temperature and that presented so far in the different chemical forms.^7Be atom can penetrate into the C_<60> to produce ^7Be@C_<60> by a recoil process of the nuclear reactions, ^<12>C(γ , α n)^7Be or ^7Li(p,n)^7Be. Radioactive endohedral fullerenes produced by the nuclear recoil, namely ^7B@C_<60>, were detected using radiochemical and radiochromatographic techniques in the final solution. To measure the decay constant of ^7Be encapsulated in the cage, ^7B@C_<60>, the same apparatus in a system (Ge-detector, MCA, Computer, etc.) was used. Furthermore, an automated sample-exchange system were installed in this term for the reduction of systematical errors. Data were collected at 8 hours intervals in the MCA system. Analysis was performed using by a least-squares fitting with the CERN program, PAW. Finally we obtained the life-time of 52.98±0.05 day for 6K and 51.97±0.05 for normal temperature, respectively. It seems that a relatively large change was obtained compared to the value resented so far.