Cross section of direct three-body breakup of ⁹Be for 1576-keV gamma rays

Abstract

Using 1576-keV γ-rays from 142Pr, the cross section of the direct three-body breakup of 9Be was measured and found to be (4.0 ± 1.8) × 10−1 μb. This result is in approximate agreement with Salyers' theoretical estimate based upon a cluster model of 9Be.

Search for the three-body photodisintegration of Be

“…It has been learned [10] from one of the authors of Ref. [5] that the 142 Pr source was made by irradiating pure Pr metal in a reactor. Since Pr has Z = 59 and gold has Z = 79, a Z 2 correction leads to a prediction that 142 Pr ␤ rays on Pr would produce 1.9 ϫ 10 −5 photons per decay above the two-body threshold.…”

“…[5]. Although the authors noted that the average energy of the 142 Pr ground-state ␤ rays is 833 keV, well below the two-body threshold, they concluded that the bremsstrahlung from ␤ rays should not play a role in the neutron yield.…”

“…Some years later (1983) Fujishiro et al [5] claimed to have actually observed neutrons from the 9 Be+ ␥ → ␣ + ␣ + n reaction induced by 1575.7-keV ␥ rays from 142 Pr decay. The neutron yield decayed with the 19-h half-life of 142 Pr and a cross section of 0.40͑18͒ b was derived.…”

“…[5], a survey was made to look for a practical radioactive source that would emit ␥ rays with energies 10 or more keV above the three-body threshold but with no radiations whatsoever above the two-body threshold. No activity meeting these requirements could be found.…”

“…[5] could be attributed to bremsstrahlung from the ␤ rays of 142 Pr. Figure 1 is a schematic drawing of the experimental arrangement for the neutron measurements.…”