Speaker
Description
The rapid neutron capture process, $\textit{r}$ process, is an important pillar of stellar nucleosynthesis, which is responsible for the production of more than half of the elements heavier than iron. However, the physical conditions and astronomical sites for $\textit{r}$ process have not been determined because of the lack of experimental data for the properties of involving exotic nuclei.
One of the critical isotopic regions in $\textit{r}$ process is the area near $^{132}$Sn, which has the neutron magicity with 82 neutrons. A drastic decrease of 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 $\textit{r}$-process conditions and make the calculation of final elemental abundance of $\textit{r}$ 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 reacted heavy 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($\textit{d}$,$\textit{p}$) 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. The features of this experiment and the preliminary results on the identified Sn isotopes after the $^{130}$Sn($\textit{d}$,$\textit{p}$) reaction will be presented.
