One- and two-neutron removal reactions from the most neutron-rich carbon isotopes

N. Kobayashi, T. Nakamura, J. A. Tostevin, Y. Kondo, N. Aoi, H. Baba, S. Deguchi, J. Gibelin, M. Ishihara, Y. Kawada, T. Kubo, T. Motobayashi, T. Ohnishi, N. A. Orr, H. Otsu, H. Sakurai, Y. Satou, E. C. Simpson, T. Sumikama, H. TakedaM. Takechi, S. Takeuchi, K. N. Tanaka, N. Tanaka, Y. Togano, K. Yoneda

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87 Citations (Scopus)

Abstract

The structure of 19,20,22C has been investigated using high-energy (around 240 MeV/nucleon) one- and two-neutron removal reactions on a carbon target. Measurements were made of the inclusive cross sections and momentum distributions for the charged residues. Narrow momentum distributions were observed for one-neutron removal from 19C and 20C and two-neutron removal from 22C. Two-neutron removal from 20C resulted in a relatively broad momentum distribution. The results are compared with eikonal-model calculations combined with shell-model structure information. The neutron removal cross sections and associated momentum distributions are calculated for transitions to both the particle-bound and particle-unbound final states. The calculations take into account the population of the mass A-1 reaction residues A-1C and, following one-neutron emission after one-neutron removal, the mass A-2 two-neutron removal residues A-2C. The smaller contributions of direct two-neutron removal, that populate the A-2C residues in a single step, are also computed. The data and calculations are shown to be in good overall agreement and consistent with the predicted shell-model ground-state configurations and one-neutron overlaps with low-lying states in 18-21C. These suggest significant νs1/22 valence neutron configurations in both 20C and 22C. The results for 22C strongly support the picture of 22C as a two-neutron halo nucleus with a dominant νs1/22 ground-state configuration.

Original languageEnglish
Article number054604
JournalPhysical Review C - Nuclear Physics
Volume86
Issue number5
DOIs
Publication statusPublished - 2012 Nov 5

ASJC Scopus subject areas

  • Nuclear and High Energy Physics

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