Population ofBe13in a nucleon exchange reaction

Abstract

The neutron-unbound nucleus 13 Be was populated with a nucleon-exchange reaction from a 71 MeV/u secondary 13 B beam. The decay energy spectrum was reconstructed using invariant mass spectroscopy based on 12 Be fragments in coincidence with neutrons. The data could be described with an s-wave resonance at Er = 0.73(9) MeV with a width of Γr = 1.98(34) MeV and a d-wave resonance at Er = 2.56(13) MeV with a width of Γr = 2.29(73) MeV. The observed spectral shape is consistent with previous one-proton removal reaction measurements from 14 B.

Neutron correlations in the decay of the first excited state of 11Li

“…The relative cross-section for nucleon exchange was an order of magnitude smaller than the 1p knockout, consistent with Ref. [37]. Based on this test case, we estimate that our simulation of single neutron scattering cross-talk is accurate within 33%.…”

“…Although we expect the majority of the events with two neutron interactions to be caused by a single neutron scattering, there could be a small contribution from a nucleon-exchange reaction that would populate 13 Be and then decay via the emission of two neutrons. Marks, et al found that such a reaction occurred with a cross-section one order of magnitude smaller than one-proton knockout in this region [37]. Assuming that this reaction was also the cause of the small background necessary for fitting the ungated two-body decay energy spectrum, we used the simulation reported in Ref.…”

“…Assuming that this reaction was also the cause of the small background necessary for fitting the ungated two-body decay energy spectrum, we used the simulation reported in Ref. [37] to replace the Maxwellian background distribution and fit the data once again (Figure 4). This simulation not only reproduces the first three decay energy spectra but gives a noticeably better description of the causality-gated three-body decay energy spectrum.…”

“…Figure 4: Decay energy spectra in coincidence with an 11 Be daughter fragment were used to verify the simulation of neutron scattering. Replacing the Maxwellian distribution shown in Figure 3 with a two-neutron decay resulting from a nucleon-exchange reaction [37] improves the reproduction of the three-body decay energy spectrum with causality cuts (d). The data shown are the same as Figure 3, but here, the dashed blue line shows a single resonance and the dot-dashed purple line shows a two-neutron decay distribution resulting from a nucleon-exchange reaction as used in Ref.…”

“…The data shown are the same as Figure 3, but here, the dashed blue line shows a single resonance and the dot-dashed purple line shows a two-neutron decay distribution resulting from a nucleon-exchange reaction as used in Ref. [37] and as discussed in the text. The black line shows the sum of the two distributions.…”