Isotopic-Spin Selection Rule Violation in the B10(d, α)Be8 Reaction

J. R. Erskine and C. P. Browne
Phys. Rev. 123, 958 – Published 1 August 1961
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Abstract

All previous tests of the isotopic-spin selection rule in (d, α) reactions were obscured by statistical weight factors because in each case the initial and final nuclear states had spin and parity 0+. The B10(d, α)Be8 reaction provides a test of the isotopic-spin selection rule free from this restriction. The energy levels of Be8 near the lowest T=1 level were studied with the Li6(He3, p)Be8 and Be9(He3, α)Be8 reactions as well as with the B10(d, α)Be8 reaction. Energy levels in Be8 were found at 16.623±0.010 Mev, 16.921±0.010 Mev, and 17.637±0.006 Mev. The widths are 95±20 kev, 85±20 kev, and <15 kev, respectively. The first of these levels is the lowest T=1 state, whereas the second is T=0 and the third probably T=1. Energy levels at 16.08 Mev and a J=2 level at 17.7 Mev, reported by other laboratories, were not observed. The ratio of the differential cross sections for formation of the 16.62- and 16.92-Mev levels was measured over a range of angles and bombarding energies. The ratio is about 1.4 and is roughly constant for both the Li6(He3, p)Be8 and B10(d, α)Be8 reactions. This implies complete violation of the selection rule because the latter reaction should not go to the T=1 level. Arguments are given which indicate that the T=0 impurities in the 16.62-Mev T=1 level are probably quite small. Consequently, the failure of the selection rule probably results from the complete intermixing of T=0 and T=1 states in the C12 compound nucleus near 28-Mev excitation. Groups from the C12(He3, p)N14 reaction were seen corresponding to levels in N14 at 5.691±0.008, 5.834±0.008, 6.203±0.008, and 6.440±0.008 Mev.

  • Received 28 March 1961

DOI:https://doi.org/10.1103/PhysRev.123.958

©1961 American Physical Society

Authors & Affiliations

J. R. Erskine* and C. P. Browne

  • Department of Physics, University of Notre Dame, Notre Dame, Indiana

  • *Present address: Laboratory for Nuclear Science, Massachusetts Institute of Technology, Cambridge, Massachusetts. Part of this paper was submitted as a dissertation to the University of Notre Dame in partial fulfillment of the requirements for a Ph.D. degree.

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Vol. 123, Iss. 3 — August 1961

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