Direct Mass Measurements to Inform the Behavior of ^{128m}Sb in Nucleosynthetic Environments

Area of Science:

• Nuclear astrophysics
• Nuclear structure physics

Background:

• Nuclear isomers significantly influence nuclear reactions in astrophysical events.
• The beta-decaying isomer ^{128m}Sb is critical as it intercepts the decay path of the A=128 isobar.

Purpose of the Study:

• To perform the first direct mass measurements of the ^{128}Sb isomer and its ground state.
• To determine the excitation energy of the ^{128m}Sb isomer.
• To assess the impact of ^{128m}Sb on nucleosynthesis.

Main Methods:

• Utilized the Canadian Penning Trap mass spectrometer at Argonne National Laboratory for precise mass measurements.
• Measured the mass excesses of both the ground state and isomeric state of ^{128}Sb.

Main Results:

• Determined the mass excesses for ^{128}Sb ground state and isomer as -84608.8(21) keV and -84564.8(25) keV, respectively.
• Calculated the excitation energy of the ^{128m}Sb isomer to be 43.9(33) keV.
• Provided the first critical nuclear data for ^{128m}Sb.

Conclusions:

• The measured masses and excitation energy of ^{128m}Sb offer essential data for nuclear astrophysics.
• ^{128m}Sb plays a significant role in the rapid neutron-capture process, affecting nucleosynthesis pathways.