Particle decays of levels in N11,12 and O12 investigated with the

Abstract

Particle-decaying states of the light nuclei 11,12 N and 12 O were studied using the invariant-mass method. The decay energies and intrinsic widths of a number of states were measured, and the momentum correlations of three-body decaying states were considered. A second 2p-decaying 2 + state of 12 O was observed for the first time, and a higher energy 12 O state was observed in the 4p+2α decay channel. This 4p+2α channel also contains contributions from fission-like decay paths, including 6 Beg.s.+ 6 Beg.s.. Analogs to these states in 12 O were found in 12 N in the 2p+ 10 B and 2p+α+ 6 Li channels. The momentum correlations for the prompt 2p decay of 12 Og.s. were found to be nearly identical to those of 16 Neg.s., and the correlations for the new 2 + state were found to be consistent with sequential decay through excited states in 11 N. The momentum correlations for the 2 + 1 state in 12 O provide a new value for the 11 N ground-state energy. The states in 12 N/ 12 O that belong to the A=12 isobaric sextet do not deviate from the quadratic isobaric multiplet mass equation (IMME) form.

Nucleon-nucleon correlations in the extreme oxygen isotopes

“…g.s. of 12 O resembles that of 16 Ne (a 2p emitter located in the sd-shell), but dramatically differs from correlations measured in p-shell nuclei such as 6 Be [20]. This indicates there might be some structural similarity of the configurations of the valence protons in 12 O and 16 Ne.…”

“…The minor differences between the experimental data and the Monte Carlo filtered calculations where the experimental acceptance and resolution is added to the time-dependent predictions could likely be reduced by modification of the employed original Minnesota force used for the nucleonnucleon interaction. Another interesting aspect is that, unlike 6 Be (see Fig 13(a) in [20]), there is a low-energy peak in the E pp correlation of 12 O. As distinct diproton emission during the time evolution is not expected, a low-E pp correlation does not necessarily correspond to diproton decay.…”

“…2p decay of proton-rich oxygen isotopes.-The proton dripline is located relatively close to the line of β stability. As a result, 2p correlation data have been obtained is several cases [20,41]. In particular, the recently measured energy correlation of the emitted protons from the x /µx + k 2 y /µy is the total momentum and µx (µy) is the reduced mass.…”

“…Its even-even neighbor, 12 O, is also a 2p emitter [18,19]. Its measured energy and angular 2p correlations [20] are rather different from those observed in 6 Be [21]. Another extreme oxygen isotope is the weakly neutron-unbound 26 O, with 18 neutrons, which is arguably the best current candidate for the phenomenon of 2n radioactivity [22][23][24][25][26][27][28][29].…”

“…The calculated 2p correlations (TD and MC) are compared with experimental data (Exp) of Ref. [20]. A is the mass number and k1, k2, and kc are the momenta of the nucleons n1 and n2, and the core c, respectively in the c.m.…”