Search

The one-neutron knock-out reaction ¹H(20C, 19Cγ) was studied at RIKEN using the DALI2 array. A γ-ray transition was observed at 198(10) keV. Based on the comparison between the experimental production cross section and theoretical predictions, the transition was assigned to the de-excitation of the 3/21+ state to the ground state. [ABSTRACT FROM AUTHOR]

A search for isomeric γ decays among fission fragments from 345 MeV/nucleon 238U has been performed at the RIKEN Nishina Center RI Beam Factory. Fission fragments were selected and identified using the superconducting in-flight separator BigRIPS and were implanted in an aluminum stopper. Delayed γ rays were detected using three clover-type high-purity germanium detectors located at the focal plane within a time window of 20 ps following the implantation. We identified a total of 54 microsecond isomers with half-lives of ~0.1--10 μ, including the discovery of 18 new isomers in very neutron-rich nuclei: 59Tim, 90Asm, 92Sem, 93Sem 94Brm 95Brm 96Brm 97Rbm 108Nbm 109Mom 117Rum 119Rum 120Rhm, 122Rhm, 121Pdm, 124Pdm 124Agm, and 126Agm, and obtained a wealth of spectroscopic information such as half-lives, γ-ray energies, γ-ray relative intensities, and γγ coincidences over a wide range of neutron-rich exotic nuclei. Proposed level schemes are presented for 59Tim, 82Gam, 92Brm, 94Brm, 95Brm, 97Rbm, 98Rbm, 108Nbm 108Zrm, 109Mom 117Rum, 119Rum, 120Rhm, 122Rhm 121Pdm 124Agm, and 125Agm, based on the obtained spectroscopic information and the systematics in neighboring nuclei. The nature of the nuclear isomerism is discussed in relation to the evolution of nuclear structure. [ABSTRACT FROM AUTHOR]

One- and two-neutron removal reactions from 19C and 20C have been studied using a liquid-hydrogen target at 40A MeV. A small cross section has been observed in the one-neutron removal reaction from 20C. The observed inclusive removal cross sections are compared with theoretical removal cross sections calculated by using shell model spectroscopic factors and Glauber-model single-particle cross sections. The observed momentum distributions are also compared with those calculated by using continuum-discretized coupled-channel methods. Good consistency between theory and experiment is shown in the one-neutron removal reaction from 19C. However, our theoretical calculation fails to reproduce the neutron removal reactions from 20C, which suggests that further improvements of the theoretical descriptions are necessary. [ABSTRACT FROM AUTHOR]