Jacque Raynal, ECIS, and $$M_n/M_p$$ M n / M p values in radioactive nuclei
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Regular Article - Experimental Physics
Jacque Raynal, ECIS, and Mn /M p values in radioactive nuclei P. D. Cottle1,a , K. W. Kemper1, L. A. Riley2 1 2
Department of Physics, Florida State University, Tallahassee, FL 32306, USA Department of Physics and Astronomy, Ursinus College, Collegeville, PA 19426, USA
Received: 21 July 2020 / Accepted: 8 September 2020 © Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Communicated by Nicolas Alamanos
Abstract Jacque Raynal’s coupled channels code ECIS has played an important role in the effort to search for shell effects in exotic isotopes using both intermediate energy Coulomb excitation and inverse kinematics proton scattering to probe their level structures and to extract neutron and proton excitation modes through their Mn /M p values. It will continue to be an important tool as nuclei very far from the stable ones are produced in new exotic beam accelerator centers.
1 Introduction The energy of the 21+ state and the electromagnetic matrix + element B(E2; 0+ gs → 21 ) are very useful in identifying even-even nuclei that have closed shells of either protons or neutrons. However, about forty years ago Bernstein, Brown and Madsen [1] demonstrated that the ratio of the neutron and proton transition matrix elements (generally written as + Mn /M p ) for the 0+ gs → 21 transition provides a complementary way of testing shell closures in stable nuclei. The quantity Mn /M p has proven to be important for testing shell closures in radioactive nuclei as well. While the magic numbers 2, 8, 20, 28, 50, 82 and 126 for stable nuclei were identified 70 years ago [2], experiments with radioactive isotopes and beams have demonstrated that the magic numbers can be different in nuclei that are not located in the valley of stability. To make determinations of Mn /M p in stable nuclei, results from experimental probes such as sub-Coulomb barrier heavy-ion scattering (Coulomb excitation) and inelastic proton scattering were compared with each other. To determine Mn /M p in neutron- and protonrich nuclei, these stable beam techniques were adapted into new techniques for use with radioactive beams-intermediateenergy Coulomb excitation and inverse kinematics proton scattering. The reaction code ECIS, developed by Jacques a e-mail:
[email protected] (corresponding author)
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Raynal [3], played a critical role in enabling this transition to radioactive beam measurements so that shell effects could be explored outside of the valley of stability.
2 Coulomb excitation One important property of a nucleus is the strength of the excitation of its states through the electromagnetic process which can then be compared to existing nuclear structure models. One method of extracting these values since the mid-1950s for stable nuclei is by carrying out scattering with charged probes that are below the systems Coulomb barrier so that uncertainties in the nuclear interaction potentials do not add ambiguity to the extracted electromagnetic strength
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