Gamma decay of high spin states in Mg25 above 6.1 MeV
New high spin states in Mg25 (up to 13.3 MeV in excitation) have been located using the N12,p)25Mg reaction at a laboratory beam energy of 23.5 MeV. Gamma decay from 28 neutron unbound levels has been observed (24 of which are reported here for the first time) up to 7 MeV above the neutron drip line. Tentative identification of the yrast line up to (17/2+ has been made, along with an extension of the ground-state rotational band up to (15/2+ and the location of several other states with J=(11/2+ and (15/2+. Extensive comparison with the s-d shell model and the cranked Nilsson-Strutinsky model has been made for the states in Mg25. Very good agreement is observed between the shell model and experimental level energies and -decay branches. Potential energy surfaces for J=(11/2+, (13/2+, and (17/2+ in the cranked Nilsson-Strutinsky model show a noncollective oblate local minimum at (μ2,)=(0.34,60°) for (11/2+ and prolate configurations at (0.2,-120°) for (13/2+ and (17/2+. These states compete with the collective ground-state band members at 0 and become yrast for (17/2+. The stabilization of these prolate aligned states relative to more deformed, collective states of the same spin results from shell effects at high spin in the cranking model, and provides a description of the configuration in the yrast 8+; (11/2+, (13/2+, and (17/2+; and 4+ states in Mg24, Mg25, and Mg26, respectively. © 1988 The American Physical Society.
Headly, DM; Sheline, RK; Tabor, SL; Httmeier, UJ; Gross, CJ; Moore, EF; Wildenthal, BH; Weller, HR; Whitton, RM; Ragnarsson, I
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