Thomas Chillery
(LUNA, LNGS)
The rapid neutron capture process, r-process, is responsible for the production of more than half of the elements heavier than iron. However, the physical conditions and astronomical sites of the r-process have not yet been determined. One key issue is the lack of experimental data on the properties of involved exotic nuclei, partly due to the difficulty of measuring neutron capture reactions for short-lived nuclei.
One of the critical isotopic regions in r-process is the area near $^{132}$Sn, which has the neutron magicity with 82 neutrons. A drastic decrease in the neutron capture rate when crossing the neutron magic number is expected for the compound neutron capture due to the large energy gap after the shell closure. Due to a lack of experimental data, there are large uncertainties in neutron capture rates, which result in the large ambiguity in r-process conditions and make the calculation of final elemental abundance of r-process undetermined.
The neutron capture rates can usually be determined with the knowledge of $\gamma$-emission probabilities of the neutron unbound states. However, the low $\gamma$-emission probabilities and usually low $\gamma$-ray detection efficiency have been the experimental obstacles. At the OEDO-SHARAQ beamline in RIKEN RIBF, an alternative method to identify experimental $\gamma$-emission probability was developed, in which the heavy reaction residues are identified with the SHARAQ spectrometer, and the $\gamma$-emission probability can be obtained based on the number of heavy residues with increased neutron number. A $^{130}$Sn(d,p) experiment was conducted with this method to identify the $\gamma$-emission probabilities of the neutron unbound states in $^{131}$Sn. The kinetic energy of $^{130}$Sn beam was degraded to about 20 MeV/u for the one neutron transfer reaction at OEDO beamline. We identified Sn isotopes with A = 129, 130, and 131, which correspond to two, one, and zero neutron emissions after the reaction, respectively, and the $\gamma$-emission probability near the one-neutron separation energy of $^{131}$Sn was explored. The features and preliminary results of this experiment will be presented.
Dr
Sunghan Bae
(Center for Nuclear Study, the University of Tokyo)
Prof.
Nobuaki Imai
(Center for Nuclear Study, the University of Tokyo)
Thomas Chillery
(LUNA, LNGS)
Shin'ichiro Michimasa
(Center for Nuclear Study, the University of Tokyo)
Daisuke Suzuki
(RIKEN Nishina Center)
Deuk Soon AHN
(Center for Exotic Nuclear Studies, IBS)
Kyungyuk Chae
(Sungkyunkwan University)
Silvio CHERUBINI
(University of Catania)
Marco La Cognata
(INFN-LNS)
M. Dozono
(Kyoto University)
M. Egeta
(Tohoku University)
F. Endo
(Tohoku University)
N. Fukuda
(RIKEN Nishina Center)
T. Haginouchi
(Tohoku University)
Shutaro Hanai
(Center for Nuclear Study, the University of Tokyo)
Seiya Hayakawa
(Center for Nuclear Study, the University of Tokyo)
Jongwon Hwang
(Center for Nuclear Study, the University of Tokyo)
Yuto Hijikata
(Kyoto University)
S. Ishio
(Tohoku University)
Naohito Iwasa
(Department of Physics, Tohoku University)
K. Kawata
(Center for Nuclear Study, the University of Tokyo)
Shigeru Kubono
R. Kojima
(Center for Nuclear Study, the University of Tokyo)
Livio LAMIA
(UniCT & INFN-LNS)
Jiatai Li
(Center for Nuclear Study, the University of Tokyo)
N. Nishimura
(Center for Nuclear Study, the University of Tokyo)
Kodai Okawa
(Center for Nuclear Study, the University of Tokyo)
HOOI JIN ONG
(Institute of Modern Physics, Chinese Academy of Sciences)
S. Ota
(RCNP, Osaka University)
Sara Palmerini
(University of Perugia and INFN Perugia, Italy)
Rosario Gianluca Pizzone
(University of Catania and Istituto Nazionale di Fisica Nucleare)
T. Saito
(Center for Nuclear Study, the University of Tokyo)
Yohei SHIMIZU
(RIKEN Nishina Center)
S. Shimoura
(Center for Nuclear Study, the University of Tokyo)
Toshiyuki Sumikama
(RIKEN Nishina Center)
Hiroshi Suzuki
(RIKEN Nishina Center)
H. Takeda
(RIKEN Nishina Center)
A. Tumino
(Kore Univ. of Enna)
X. Tang
(Institute of Modern Physics, Chinese Academy of Sciences)
H. Tanaka
(Kyushu University)
M. Tanaka
(RIKEN Nishina Center)
T. Teranishi
(Kyushu University)
Y. Togano
(RIKEN Nishina Center)
Rin Yokoyama
(Center for Nuclear Study, the University of Tokyo)
R. Yoshida
(INFN, LNS)
Koichi Yoshida
(RIKEN Nishina Center)
Masahiro Yoshimoto
(RIKEN Nishina Center)
Y. Wang
(Tsinghua University)
Z. Xiao
(Tsinghua Univ.)
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