Interplay between sequential and prompt two-proton decay from the first excited state ofNe16

Abstract

The first-excited, J π = 2 + state of 16 Ne at E * = 1.69(2) MeV is well populated in neutron knockout reactions with a 17 Ne beam and the correlations between the momenta of the three final fragments following 2p decay were measured. The correlation pattern showed aspects of both sequential and diproton-like decay, which were reproduced in three-body 14 O+p+p calculations. These calculations suggest that interference between these processes is responsible for the observed features which can be described in terms of a "tethered decay mechanism". The intrinsic width of this state was constrained to be from 100 to 250 keV. Higher excited states populating the 13 N+p+p+p exit channel were found at E

Spin alignment following inelastic scattering of Ne17 , lifetime of F16 , and its constraint on the continuum coupling strength

“…The detected 17 Ne * →2p+ 15 O events were produced only from the 17 Ne component of the beam as verified from their reconstructed center-of-mass velocity which were similar to the higher 17 Ne beam velocity. The excitation-energy spectrum of 17 Ne fragments obtained from 2p+ 15 O events has been described in [20]. Figure 2(a) shows this spectrum (circles) only in the vicinity of the peak associated with the 2 nd excited state.…”

“…Rather, it appears the second proton retains a memory of the emission direction of the first proton. Probably we are observing a much milder version of the decay correlations found for the first excited state (J π =2 + 1 ) state in 16 Ne where the energies of the protons are consistent with sequential decay, but the θ pp distribution is strongly enhanced for small relative angles [20]. Further experimental and theoretical efforts are needed to better understand this effect.…”

“…The experiment was performed at the Coupled Cyclotron Facility at the National Superconducting Cyclotron Laboratory at Michigan State University. Details have been published elsewhere [18][19][20]. Briefly, a mixed 17 Ne(E/A=62.9 MeV, 11%, 1.6×10 4 pps)- 15 O(E/A=52.1 MeV, 89%) secondary beam was produced from a primary 16 O beam (E/A=150 MeV, 175 pnA).…”

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

“…The present dineutron model is a strong simplification of a complex decay mechanism, especially for neutron unbound states which decay on a very short time scale. A full threebody model similar to the recently developed three-body cluster model used to explain correlations in the two-proton of 6 Be and 16 Ne could aid in further distinguishing this decay mechanism [21,47] and with it, the central energy of this state.…”

Three-body correlations in direct reactions: Example of Be6 populated in the ( p,n ) reaction

“…Studies of the three-body correlations for decays [18][19][20] or particle emission from states populated in reactions [3][4][5]21,22] are quite active in the recent years. In such studies the experimental question arises, which should be resolved to make theoretical interpretation possible: How much are the observed correlation patterns different from the actual?…”