Elsevier

Nuclear Physics A

Volume 146, Issue 1, 4 May 1970, Pages 136-148
Nuclear Physics A

Decay modes of 9Li and states of 9Be

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Abstract

The β-decay of the 9Li nucleus and the subsequent particle decays of the unbound states of the 9Be nucleus have been investigated with two complementary techniques, a recoil-particle method and a beta-neutron coincidence method. 9Li nuclei were produced by the 18O(7Li, 9Li) 16O reaction at a bombarding energy of 20 MeV and by the 3H(7Li, 9Li)p reaction with a 14 MeV bombarding energy. The energy spectrum of the delayed alphas and the time-of-flight spectrum of the delayed neutrons were obtained. The half-life was measured to be 177±3 ms. Besides the known decay branches to the ground state and to the 2.43 MeV state in 9Be, a new decay branch to an unbound state in 9Be at an excitation energy of 2.78±0.12 MeV was observed. The branching ratios and the log ft values were found to be (65.0−2.4+2.7) %, (32.0−3.7+2.7)%, (3.0−0.3+2.7)% and 5.12−0.02+0.01, 5.00−0.05+0.04, 5.97−0.28+0.05 to the ground state, the 2.43 MeV state and the 2.78 MeV state, respectively. The observed properties of the 2.78 MeV state favor an assignment of 12. This state decays mainly by neutron emission to the ground state of 8Be and has a c.m. width of 1.10±0.12 MeV.

The fraction of the decays of the 2.43 MeV state in 9Be involving emission of a neutron to the ground state of 8Be was found to be (6.4±1.2)%.

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Supported in part by the National Science Foundation [GP-9114] and by the Office of Naval Research [Nonr-220(47)].

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