One-neutron knockout from light neutron-rich nuclei at relativistic energies

Abstract

One-neutron knockout reactions from neutron-rich nuclei, with Z = 6−13 and N = 8−22, were studied at the Fragment Separator (GSI) at high beam energies, around 700 MeV/nucleon. Structural phenomena such as the formation of one-neutron halos in odd-mass carbon isotopes ( 15,17,19 C) will be discussed. In addition, one-neutron knockout measurements from 22 N were carried out for the first time and demonstrate clearly the change from a 0d 5/2 to a 1s 1/2 orbital for the valence neutron, an effect that is expected above N = 14 and that was also observed in 23 O and 24 F. The possibility of an anomalous structure of 26 F, due to a significant 1s 1/2 neutron admixture, will also be discussed in the light of the experimental data obtained in this work. Finally, the ground-state configuration of neutron-rich neon isotopes ( 24−28 Ne) was studied, providing new information in a region that is relatively close to the island of inversion.

One-neutron removal reactions on Al isotopes around theN=20shell closure

“…Our cross sections agree with the values given in Ref. [25] for 34,35 Al and have smaller uncertainties.…”

Experimental study of the19O(d,p)20O

“…Recent evidence identifies N = 14 as a subshell closure for Z = 8 [1][2][3][4][5][6][7]. Therefore, 20 O is considered as having a ground state configuration with two neutron holes inside the 0d 5/2 orbital, allowing the calculation of (0d 5/2 ) 2 T = 1 diagonal two-body matrix elements.…”

Nuclear matter distributions in the neutron-rich carbon isotopes $^{14-17}$C from intermediate-energy proton elastic scattering in inverse kinematics

“…These results also signal the formation of a neutron halo. Narrow fragment momentum distributions of the reaction products in the nuclear break-up of 15 C [10,11,18,19], 19 C [12,19,20] and 22 C [12] support the existence of a halo structure in these nuclei.…”

“…Recently, an experimental evidence for a prevalent Z = 6 magic number in neutron rich carbon isotopes was presented [14] based on a systematic study of proton radii, electromagnetic transition rates and atomic masses of light nuclei. Small neutron separation energies are known in 15 C, 17 C, 19 C and 22 C [15], so these nuclei are suggested to be candidates to exhibit a neutron halo. Large enhancements in the values of the root-mean-square (rms) nuclear matter radius R m evaluated from the measured interaction cross sections were found for 15 C, 19 C [9,16] and 22 C [17].…”

“…Small neutron separation energies are known in 15 C, 17 C, 19 C and 22 C [15], so these nuclei are suggested to be candidates to exhibit a neutron halo. Large enhancements in the values of the root-mean-square (rms) nuclear matter radius R m evaluated from the measured interaction cross sections were found for 15 C, 19 C [9,16] and 22 C [17]. These results also signal the formation of a neutron halo.…”