High-Energy Beta Decay of Light Elements [electronic resource].
- Washington, D.C. : U.S. Atomic Energy Commission, 1958. and Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
- Additional Creators:
- U.S. Atomic Energy Commission and United States. Department of Energy. Office of Scientific and Technical Information
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- Free-to-read Unrestricted online access
- The beta decay of the radioactive members of the mass-eight and -twelve triads has been studied with a spiral-orbit spectrometer having a 1.3% resolution. The end point, half-life and log-ft values respectively are: for N¹², 16.37 ± 0.06 MeV, 11.43 ± 0.05 milliseconds, and 4.17; for B¹², 13.40 ± 0.05 MeV, 20.6 ± 0.2 msec and 4.11; for B⁸, 14 MeV (broad), 0.75 ± 0.02 sec, and 5.72; and for Li⁸, 13 Mev (broad), 0.87 ± 0.01 sec, and 5.67. The mass excesses in millimass units are: for N¹², 22.48 ± 0.06; for B¹², 18.19 ± 0.06; for B⁸, 27.08 ± 0.13; and for Li⁸, 24.97 ± 0.09. The shapes of the Kurie function for the mirror pairs indicate positron and electron transitions to the same levels of the daughter nuclide, with greater percentages in the positron branches relative to the ground-state transitions because of the higher energy available. The Li⁸ and B⁸ shapes are consistent with the shape of the alpha spectrum following the decay of the Be⁸ daughter. Less than 1% of the Li⁸ transition and less than 5% of the B⁸ transition go to the Be⁸ ground state. Besides the main transition to the broad 2.9-Mev level, a broad level near 11 Mev is probably involved. The ft values and the assumption of J = 0, 2, and 4 levels in Be⁸ favor J = 3 for Li⁸ and B⁸. The N¹² and B¹² spectra indicate transitions of a few percent to the 4.43- and 7.65-Mev levels in C¹², with higher levels not excluded. For these nuclides J = 1 is favored. The agreement of the measured end points and resulting Q values with published values shows that the spiral-orbit spectrometer can be accurately calibrated with only the theory as a guide. Another evaluation of the spectrometer is that the measured shape of the B¹². Kurie function is the same within statistics as that obtained elsewhere with a ring-focus magnetic-lens spectrometer.
- Published through SciTech Connect., 06/16/1958., "ucrl--8324", Vedder, James F., and Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
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