Studies on the Low-Lying Levels ofNe24

Abstract

Formation of the ground and 4.76-MeV Ne'4 states is characterized by 1=0 transfer, which establishes J =0+ for these two states. The J=2, 3.87-MeV state was observed to be formed via l=2 transfer, and so even parity is indicated for this state. Proton-y angular-correlation experiments were carried out in method II geometry at 8&=3. 45 and 3.33 MeV. These results establish unambiguous J=4 and 2 assignments for the respective 3.96and 5.58-MeV levels of Ne'4. The present experimental information on the static properties of Ne is shown to be consistent with a j-j coupling-model representation involving pure twobody proton condgurations. An intercomparison of the observed static properties associated with the low-lying levels of the even-A neon isotopes is presented, and a remarkable similarity is shown to exist between the low-lying level structures of 0" and Ne". It is concluded that 1dsg~subshell closure effects underlie the Ne" spectrum.(and perhaps nine) states in Ne 4 below E, =6.04 MeV via magnetic-spectrograph studies at a fixed angle (8~=90') with energy resolution of &20 keV; (b) Becker, Chase, McDonald, and Warburton' have further established both static and dynamic properties for the 1.99-, 3.87-, and 4.76-MeV Ne'4 levels. This previously available information is summarized in Fig. 1.The present work is primarily concerned with the four Ne" states between E,=3.96 and 5.58 MeV. Angular-distribution measurementswere carried out on the protons from the Ne" (1, P) Ne'4 reaction studied at E& --3.30 MeV and are reported in Sec. II. Protongamma angular-correlation studies were performed on the Ne" (1 Py) Ne" reaction at 8, = 3.45 and 3.33 MeV, and these experiments are presented in Sec. III. The implications associated with the known information on this T, = 2 member of the A = 24 system are discussed in Sec. IV, in which a comparison is also made involving the known static properties of the low-lying levels of the even-A neon isotopes.

Two-neutron knockout from neutron-deficientAr34,S30Yoneda1, Obertelli2, Gade3 et al. 2006Phys. Rev. C669450View full textAdd to dashboardCite

“…The projectiles of interest- 34 Ar, 30 S and 26 Si-were produced by fragmentation of a 150 MeV/nucleon 36 Ar primary beam provided by the Coupled Cyclotron Facility of the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University. The 9 Be production target was located at the mid-acceptance target position of the Energy thresholds of the direct and two-step processes in the 9 Be( 34 Ar, 32 Ar)X two-neutron removal reaction.…”

“…J π f E exp (keV) σ exp (mb) σ th (mb) str (%) str-diff (%) diff (%) 34 Ar 0 + gs 0 0.41 (7) (10) in which both of the tightly-bound nucleons are removed by elastic dissociation.…”

“…The measured B 0 are compared to two model calculations. The first assumes the knockout of two completely uncorrelated neutrons from pure configurations ν[d 5 34 Ar, respectively (see, e.g., Section III of Ref. [24]).…”

“…In summary, two-neutron knockout reaction measurements have been performed on the already neutron-deficient nuclei 34 Ar, 30 S, and 26 Si, near the proton dripline. Particle-γ coincidences allowed the measurement of the partial cross sections to individual bound final states.…”

Spectroscopic study of the exotic nucleusP25

“…All the other excited states have, in addition, a third decay channel with the 24 Si produced in its second excited state, observed at 3.441 MeV [30]. The spin and parity of this excited state are not known but two states are known in its mirror nucleus 24 Ne near this energy: a 2 + state at 3.868 MeV and a 4 + at 3.972 MeV [31]. It would be natural to expect the existence of the mirror analogs of both of these states in 24 Si.…”