First application of mass measurement with the Rare-RI Ring reveals the solar r-process abundance trend at A=122 and A=123

Abstract

The Rare-RI Ring (R3) is a recently commissioned cyclotron-like storage ring mass spectrometer dedicated to mass measurements of exotic nuclei far from stability at Radioactive Isotope Beam Factory (RIBF) in RIKEN. The first application of mass measurement using the R3 mass spectrometer at RIBF is reported. Rare isotopes produced at RIBF, ${}^{127}$Sn, ${}^{126}$In, ${}^{125}$Cd, ${}^{124}$Ag, ${}^{123}$Pd, were injected in R3. Masses of ${}^{126}$In, ${}^{125}$Cd, and ${}^{123}$Pd were measured whereby the mass uncertainty of ${}^{123}$Pd was improved. This is the first reported measurement with a new storage ring mass spectrometery technique realized at a heavy-ion cyclotron and employing individual injection of the pre-identified rare nuclei. The latter is essential for the future mass measurements of the rarest isotopes produced at RIBF. The impact of the new ${}^{123}$Pd result on the solar $r$-process abundances in a neutron star merger event is investigated by performing reaction network calculations of 20 trajectories with varying electron fraction $Y_e$. It is found that the neutron capture cross section on ${}^{123}$Pd increases by a factor of 2.2 and $\beta$-delayed neutron emission probability, $P_{1n}$, of ${}^{123}$Rh increases by 14\%. The neutron capture cross section on ${}^{122}$Pd decreases by a factor of 2.6 leading to pileup of material at $A=122$, thus reproducing the trend of the solar $r$-process abundances. The trend of the two-neutron separation energies (S${}_{2n}$) was investigated for the Pd isotopic chain. The new mass measurement with improved uncertainty excludes large changes of the S${}_{2n}$ value at $N=77$. Such large increase of the S${}_{2n}$ values before $N=82$ was proposed as an alternative to the quenching of the $N=82$ shell gap to reproduce $r$-process abundances in the mass region of $A=112-124$.

References in corpus (11)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• Multi-messenger Observations of a Binary Neutron Star Merger
• The r-process of stellar nucleosynthesis: Astrophysics and nuclear physics achievements and mysteries
• Surface diffuseness correction in global mass formula
• Identification of strontium in the merger of two neutron stars
• Dynamical r-process studies within the neutrino-driven wind scenario and its sensitivity to the nuclear physics input
• Advanced LIGO Constraints on Neutron Star Mergers and R-Process Sites
• Neutron-gamma competition for $\beta$-delayed neutron emission
• First glimpse of the $N=82$ shell closure below $Z=50$ from masses of neutron-rich cadmium isotopes and isomers
• Following nuclei through nucleosynthesis: a novel tracing technique
• Development and operation of an electrostatic time-of-flight detector for the Rare RI storage Ring

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