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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.
Abstract:
This manuscript reports on the direct observation of a β-delayed two-neutron emission in a study of ^{134}In at the ISOLDE Decay Station using neutron spectroscopy. We also report on the first measurement in β^{-} decay of the long-sought 13/2^{+} excited state in ^{133}Sn, attributed to be the neutron single-particle i_{13/2} orbital. The observation of sequential neutron emission is used to extract the relative population of the i_{13/2} state, which was found to be much smaller than the predictions of the statistical model. The experiment was possible because of the innovative use of a neutron array with neutron discrimination and interaction tracking capabilities. This is the first study of the details of the two-neutron emission for a nucleus, which belongs to the r-process path. Understanding β-delayed two-neutron emission probabilities is essential to validate models used in astrophysical r-process nucleosynthesis calculations. Observing two-neutron emissions in β^{-} decay paves the way for new experiments to study energy and angular correlations for β-delayed multineutron emitters.
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