Abstract
A beryllium "rabbit" irradiated with neutrons from the reaction was transferred repeatedly to remote scintillation detectors by means of a timed pneumatic system. The spectrum of beta rays emitted by the Be sample and detected by means of a Pilot-B scintillator displays a strong component with a half-life of ∼1 sec and MeV and a weaker component with a half-life of 0.19±0.03 sec and MeV. These activities are identified as from the reaction and as from the reaction, respectively. A much weaker component is assigned to resulting from oxygen in the sample. Beta rays in coincidence with neutrons detected in a second Pilot-B crystal have an end-point energy of 11.0±0.4 MeV. The coincidence spectrum from the neutron-detecting crystal displays a principal component corresponding to a neutron energy of 0.7±0.2 MeV and gives some evidence for neutrons having an energy of 3-4.5 MeV. From these data, together with a shape analysis of the beta-ray singles spectrum, it is deduced that decays with a 25% branch to the ground state of and with a 75% branch mostly to the known 2.430-MeV level (). Both values require allowed transitions and are compatible with a probable shell-model spin-parity assignment of to and with the tentative assignment of given previously to the 2.430-MeV level. The cross section for forming with neutrons of about 15.5 MeV is ∼0.7 mb.
- Received 29 May 1963
DOI:https://doi.org/10.1103/PhysRev.132.328
©1963 American Physical Society