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First β-Delayed Two-Neutron Spectroscopy of the r-Process Nucleus ^{134}In and Observation of the i_{13/2}
P Dyszel1, R Grzywacz1, Z Y Xu1
1Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA.
Physical Review Letters
|October 25, 2025
Summary
Researchers directly observed beta-delayed two-neutron emission in ^{134}In, revealing a smaller-than-predicted population of a key excited state in ^{133}Sn. This finding is crucial for validating astrophysical models of nucleosynthesis.
Area of Science:
- Nuclear Physics
- Nuclear Astrophysics
Background:
- Understanding beta-delayed neutron emission is vital for nuclear astrophysics, particularly for r-process nucleosynthesis.
- Previous studies lacked detailed insights into two-neutron emission mechanisms.
Purpose of the Study:
- To directly observe beta-delayed two-neutron emission in ^{134}In.
- To measure the population of the 13/2^{+} excited state in ^{133}Sn.
- To validate nuclear statistical models used in astrophysical calculations.
Main Methods:
- Utilized neutron spectroscopy at the ISOLDE Decay Station.
- Employed an innovative neutron array with discrimination and tracking capabilities.
- Studied the beta-decay of ^{134}In.
Main Results:
- Direct observation of beta-delayed two-neutron emission.
- First measurement of the 13/2^{+} excited state in ^{133}Sn, linked to the i_{13/2} orbital.
- Observed sequential neutron emission, yielding the relative population of the i_{13/2} state.
- Found the population of the i_{13/2} state to be significantly lower than statistical model predictions.
Conclusions:
- The study provides the first detailed investigation of two-neutron emission for an r-process nucleus.
- Experimental results challenge current statistical model predictions.
- Opens new avenues for studying beta-delayed multineutron emission and its astrophysical implications.
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