Two-neutron sequential decay ofO24

Abstract

A two-neutron unbound excited state of 24 O was populated through a (d,d') reaction at 83.4 MeV/nucleon. A state at E = 715 ± 110 (stat) ±45 (sys) keV with a width of Γ < 2 MeV was observed above the two-neutron separation energy placing it at 7.65 ± 0.2 MeV with respect to the ground state. Three-body correlations for the decay of 24 O → 22 O + 2n show clear evidence for a sequential decay through an intermediate state in23 O. Neither a di-neutron nor phase-space model for the three-body breakup were able to describe these correlations.

Three-body model for the two-neutron emission ofBe16

“…In one of the first theoretical studies of twoneutron decay, Grigorenko [12] discussed the existence of one-, two-, and four-neutron emitters, as well as comparisons of their widths in a three-body framework. Recently, a few cases of two-neutron decay have been observed [13,14,15]. The first of these was observed in a 2012 experiment at the National Superconducting Cyclotron Laboratory [13] through the decay of 16 Be to 14 Be plus two neutrons.…”

“…In Section III, details about the two-and three-body potentials are presented, as well as a convergence study of our calculations. Our results, assuming either a 1d 5/2 or a 2s 1/2 ground state for 15 Be, are discussed in Section IV, and in Section V, we discuss the consequences of these models. Finally, we conclude in Section VI.…”

“…The first of these was observed in a 2012 experiment at the National Superconducting Cyclotron Laboratory [13] through the decay of 16 Be to 14 Be plus two neutrons. As the ground state energy of 16 Be was found to be 1.35 MeV (with a width of 0.8 MeV) and a lower limit of 1.54 MeV had previously been placed on the ground state of 15 Be [16], 16 Be is an ideal candidate for simultaneous two-neutron decay. Depending on the width of the ground state of 15 Be, sequential neutron de-cay from 16 Be to 14 Be could be energetically inaccessible.…”

“…As the ground state energy of 16 Be was found to be 1.35 MeV (with a width of 0.8 MeV) and a lower limit of 1.54 MeV had previously been placed on the ground state of 15 Be [16], 16 Be is an ideal candidate for simultaneous two-neutron decay. Depending on the width of the ground state of 15 Be, sequential neutron de-cay from 16 Be to 14 Be could be energetically inaccessible. A later experiment [17] determined that the lowest state in 15 Be is an l = 2 state at 1.8 MeV with a width of 575 ± 200 keV.…”

“…Depending on the width of the ground state of 15 Be, sequential neutron de-cay from 16 Be to 14 Be could be energetically inaccessible. A later experiment [17] determined that the lowest state in 15 Be is an l = 2 state at 1.8 MeV with a width of 575 ± 200 keV.…”