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Updated: Apr 22, 2026

Angle-resolved Photoemission Spectroscopy At Ultra-low Temperatures
Published on: October 9, 2012
Nuclear physics. Momentum sharing in imbalanced Fermi systems
O Hen1, M Sargsian2, L B Weinstein3
1Tel Aviv University, Tel Aviv 69978, Israel. or.chen@mail.huji.ac.il.
Abstract:
The atomic nucleus is composed of two different kinds of fermions: protons and neutrons. If the protons and neutrons did not interact, the Pauli exclusion principle would force the majority of fermions (usually neutrons) to have a higher average momentum. Our high-energy electron-scattering measurements using (12)C, (27)Al, (56)Fe, and (208)Pb targets show that even in heavy, neutron-rich nuclei, short-range interactions between the fermions form correlated high-momentum neutron-proton pairs. Thus, in neutron-rich nuclei, protons have a greater probability than neutrons to have momentum greater than the Fermi momentum. This finding has implications ranging from nuclear few-body systems to neutron stars and may also be observable experimentally in two-spin-state, ultracold atomic gas systems.
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