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Shell structure at N=28 near the dripline: spectroscopy of $^{42}$Si, $^{43}$P and $^{44}$S

J. Fridmann·I. Wiedenhoever·A. Gade·L. T. Baby·D. Bazin·B. A. Brown·C. M. Campbell·J. M. Cook·P. D. Cottle·E. Diffenderfer·D. -C. Dinca·T. Glasmacher·P. G. Hansen·K. W. Kemper·J. L. Lecouey·W. F. Mueller·E. Rodriguez-Vieitez·J. R. Terry·J. A. Tostevin·K. Yoneda·H. Zwahlen
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Abstract

Measurements of the N=28 isotones 42Si, 43P and 44S using one- and two-proton knockout reactions from the radioactive beam nuclei 44S and 46Ar are reported. The knockout reaction cross sections for populating 42Si and 43P and a 184 keV gamma-ray observed in 43P establish that the d_{3/2} and s_{1/2} proton orbits are nearly degenerate in these nuclei and that there is a substantial Z=14 subshell closure separating these two orbits from the d_{5/2} orbit. The increase in the inclusive two-proton knockout cross section from 42Si to 44S demonstrates the importance of the availability of valence protons for determining the cross section. New calculations of the two-proton knockout reactions that include diffractive effects are presented. In addition, it is proposed that a search for the d_{5/2} proton strength in 43P via a higher statistics one-proton knockout experiment could help determine the size of the Z=14 closure.

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J. Fridmann, I. Wiedenhoever, A. Gade, L. T. Baby, D. Bazin, B. A. Brown, C. M. Campbell, J. M. Cook, P. D. Cottle, E. Diffenderfer, D. -C. Dinca, T. Glasmacher, P. G. Hansen, K. W. Kemper, J. L. Lecouey, W. F. Mueller, E. Rodriguez-Vieitez, J. R. Terry, J. A. Tostevin, K. Yoneda, H. Zwahlen. 2006-08-14. Shell structure at N=28 near the dripline: spectroscopy of $^{42}$Si, $^{43}$P and $^{44}$S. https://doi.org/10.1103/physrevc.74.034313

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