One-neutron removal reactions ofC18andC19on a pro

Abstract

We have studied the one-neutron removal reactions of 18 C at 81 MeV/nucleon and 19 C at 68 MeV/nucleon on a liquid hydrogen target. Transverse-momentum distributions of the core fragments 17 C and 18 C, and their partial cross sections, are measured using coincidences with the γ rays. These are compared to theoretical calculations based on the continuum-discretized coupled-channels (CDCC) method. We have found that the transverse-momentum distributions of 17 C are well described by the CDCC calculations, and the agreement provides evidence for the spin-parity assignments of J π = 1/2 + for the 0.21-MeV state and J π = 5/2 + for the 0.33-MeV state in 17 C. The J π = (2, 3) + assignment for the 4.0-MeV state in 18 C is obtained for the first time based on the momentum distribution of 18 C. The measured partial cross sections are consistent with the CDCC calculations combined with shell-model spectroscopic factors. The present study demonstrates that the transverse-momentum distribution obtained in a one-neutron removal reaction on a proton target is as useful as the conventional longitudinal-momentum distribution measured with the heavier Be or C targets for determining the orbital angular momentum of a removed neutron.

Ab InitioCoupled-Cluster Effective Interactions for the Shell Model: Application to Neutron-Rich Oxygen and Carbon Isotopes

“…Separation energies, spin assignments for lowlying states, the energies of 2 + states, and transition rates in these isotopes all depend on the locations of shell gaps. [24][25][26][27][28][29][30][31]. At present there is no evidence for a shell closure at the N = 14 nucleus 20 C [32], despite the N = 14 shell closure at 22 O.…”

“…In 23,24 O the CCEI results start to deviate from the Λ-CCSD(T) reference values. In 24 O the CCEI ground-state is less bound by about 3.5 MeV than obtained with Λ-CCSD(T).…”

“…To understand the origin of shell structure, however, researchers are now trying to derive the shell model from realistic nucleonnucleon (NN) and three-nucleon forces (3NFs), without further phenomenology [3,10,11]. Within the last few years, for example, Otsuka et al [11] showed that 3NFs play a pivotal role in placing the drip line (correctly) in the oxygen isotopes at 24 O, and Holt et al [3] showed that the inclusion of 3NFs are necessary to explain the high 2 + state in 48 Ca .…”

“…The gray bands indicate states above the neutron decay threshold. 21,22,23,24 O. Our Λ-CCSD(T) calculations use the model space mentioned earlier, while the calculations that determine our CCEI use N max = 12 and N 1 + N 2 + N 3 = 12.…”

β-delayed neutron andγ-ray spectroscopy of17C utilizing spin-polarizedUeno1, Miyatake2, Yamamoto3 et al. 2013Phys. Rev. CSelf Cite28160View full textAdd to dashboardCite

“…Until now, the existence of three excited states has been suggested at the excitation energy values E x ∼ 210 keV [16][17][18][19], 295 keV [13,14], and 331 keV [16][17][18][19][20], below S n = 0.729(18) MeV. Investigation of these three states is a central subject for the 0n channel.…”