<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>β</mml:mi></mml:math>-Delayed One and Two Neutron Emission Probabilities Southeast of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi>Sn</mml:mi></mml:mrow><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>132</mml:mn></mml:mrow></mml:mmultiscripts></mml:mrow></mml:math> and the Odd-Even Systematics in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>r</mml:mi></mml:math>-Process Nuclide Abundances
V. H. Phong, S. Nishimura, G. Lorusso, T. Davinson, A. Estrade, O. Hall, Toshihiko Kawano, J. J. Liu, F. Montes, Nobuya Nishimura, R. Grzywacz, K. P. Rykaczewski, J. Agramunt, D. S. Ahn, A. Algora, J. M. Allmond, H. Baba, S. Bae, N. T. Brewer, C. G. Bruno, R. Caballero-Folch, F. Calviño, P. J. Coleman-Smith, G. Cortés, I. Dillmann, C. Domingo‐Pardo, A. Fijałkowska, Nobuo Fukuda, S. Go, C. J. Griffin, J. Ha, L. J. Harkness-Brennan, T. Isobe, D. Kahl, L. H. Khiem, G. Kiss, A. Korgul, S. Kubono, M. Labiche, I. Lazarus, J. F. Liang, Z. Liu, Kazunori Matsui, K. Miernik, B. Moon, A. I. Morales, P. Morrall, N. Nepal, R. D. Page, M. Piersa-Siłkowska, V. Pucknell, B. C. Rasco, B. Rubio, H. Sakuraï, Y. Shimizu, D. W. Stracener, T. Sumikama, H. Suzuki, J. L. Taı́n, H. Takeda, A. Tarifeño-Saldivia, A. Tolosa-Delgado, M. Wolińska-Cichocka, P. J. Woods, R. Yokoyama
Abstract
The $\ensuremath{\beta}$-delayed one- and two-neutron emission probabilities (${P}_{1n}$ and ${P}_{2n}$) of 20 neutron-rich nuclei with $N\ensuremath{\ge}82$ have been measured at the RIBF facility of the RIKEN Nishina Center. ${P}_{1n}$ of $^{130,131}\mathrm{Ag}$, $^{133,134}\mathrm{Cd}$, $^{135,136}\mathrm{In}$, and $^{138,139}\mathrm{Sn}$ were determined for the first time, and stringent upper limits were placed on ${P}_{2n}$ for nearly all cases. $\ensuremath{\beta}$-delayed two-neutron emission ($\ensuremath{\beta}2n$) was unambiguously identified in $^{133}\mathrm{Cd}$ and $^{135,136}\mathrm{In}$, and their ${P}_{2n}$ were measured. Weak $\ensuremath{\beta}2n$ was also detected from $^{137,138}\mathrm{Sn}$. Our results highlight the effect of the $N=82$ and $Z=50$ shell closures on $\ensuremath{\beta}$-delayed neutron emission probability and provide stringent benchmarks for newly developed macroscopic-microscopic and self-consistent global models with the inclusion of a statistical treatment of neutron and $\ensuremath{\gamma}$ emission. The impact of our measurements on $r$-process nucleosynthesis was studied in a neutron star merger scenario. Our ${P}_{1n}$ and ${P}_{2n}$ have a direct impact on the odd-even staggering of the final abundance, improving the agreement between calculated and observed Solar System abundances. The odd isotope fraction of Ba in $r$-process-enhanced ($r\text{\ensuremath{-}}\mathrm{II}$) stars is also better reproduced using our new data.