Near-yrast, medium-spin, excited states of {sup 91}Rb, {sup 93}Rb, and {sup 95}Rb

• Published in: Physical review. C, Nuclear physics Nuclear physics, 2010-08, Vol.82 (2)
• Main Authors: Simpson, G. S., Urban, W., Faculty of Physics, University of Warsaw, ul. Hoza 69, PL-00-681 Warsaw, Sieja, K., Dare, J. A., Orlandi, R., Smith, A. G., Tsekhanovich, I., Varley, B. J., Durell, J. L., Smith, J. F., Jolie, J., Linneman, A., Scherillo, A., Soldner, T., Faust, H., Zlomaniec, A., Rzaca-Urban, T., Ahmad, I., Greene, J. P.
• Format: Article
• Language: English
• Subjects: ACTINIDE NUCLEI; ALPHA DECAY RADIOISOTOPES; ANGULAR MOMENTUM; BARYON REACTIONS; BARYONS; BETA DECAY RADIOISOTOPES; BETA-MINUS DECAY RADIOISOTOPES; CALIFORNIUM 252; CALIFORNIUM ISOTOPES; CONFIGURATION; CURIUM 248; CURIUM ISOTOPES; DECAY; ELEMENTARY PARTICLES; ENERGY LEVELS; ENERGY RANGE; ENERGY-LEVEL TRANSITIONS; EVEN-EVEN NUCLEI; EVEN-ODD NUCLEI; EXCITATION; EXCITED STATES; FERMIONS; FISSION; HADRON REACTIONS; HADRONS; HALF-LIFE; HEAVY NUCLEI; INTERMEDIATE MASS NUCLEI; INTERNAL CONVERSION RADIOISOTOPES; ISOMERIC TRANSITION ISOTOPES; ISOMERS; ISOTOPES; MASS SPECTROMETERS; MATHEMATICAL MODELS; MEASURING INSTRUMENTS; MEV RANGE; MEV RANGE 01-10; MILLISECONDS LIVING RADIOISOTOPES; MINUTES LIVING RADIOISOTOPES; NEUTRON GUIDES; NEUTRON REACTIONS; NEUTRONS; NUCLEAR DECAY; NUCLEAR MODELS; NUCLEAR PHYSICS AND RADIATION PHYSICS; NUCLEAR REACTIONS; NUCLEI; NUCLEON REACTIONS; NUCLEONS; ODD-EVEN NUCLEI; PARTICLE PROPERTIES; RADIOISOTOPES; RUBIDIUM 91; RUBIDIUM 93; RUBIDIUM 95; RUBIDIUM ISOTOPES; SECONDS LIVING RADIOISOTOPES; SHELL MODELS; SPECTROMETERS; SPIN; SPONTANEOUS FISSION; SPONTANEOUS FISSION RADIOISOTOPES; URANIUM 235; URANIUM ISOTOPES; YEARS LIVING RADIOISOTOPES; YRAST STATES; YTTRIUM 97; YTTRIUM ISOTOPES
• ISSN: 0556-2813; 1089-490X
• DOI: 10.1103/PHYSREVC.82.024302

The medium-spin structure of the nuclei {sup 93}Rb and {sup 95}Rb is studied following the neutron-induced fission of {sup 235}U at the PF1B neutron guide, using the FIFI spectrometer, and at the Lohengrin mass spectrometer of the Institut Laue-Langevin Grenoble. These nuclei, plus {sup 91}Rb, are also studied following the spontaneous fission of {sup 248}Cm and {sup 252}Cf sources, using the EUROGAM-II and Gammasphere detector arrays, respectively. A high-spin isomeric state, with a half-life of 111(11) ns, is found in {sup 93}Rb at an excitation energy of 4422.4 keV, which most likely corresponds to the fully aligned [{pi}(g{sub 9/2}) x {nu}(g{sub 7/2}h{sub 11/2})]{sub 27/2}{sup -} configuration. An analogous configuration is proposed for the 5297.9-keV level observed in {sup 91}Rb. A new E3 decay branch of the 1133.9-keV isomer in {sup 91}Rb is found, for which the rather low transition rate of B(E3)=3.8(10) W.u. is determined. The energy of the isomeric state of {sup 95}Rb is now proposed to be at 810.6 keV, with a spin of (9/2{sup +}), and its half-life determined to be T{sub 1/2}=94(7) ns. A cascade of prompt transitions is observed on top of the 810.6-keV isomer in {sup 95}Rb. The near-yrast structures of {sup 91}Rb, {sup 93}Rb, and {sup 95}Rb are compared to the results of shell-model calculations, which support the proposed 27/2{sup -} interpretation of states in {sup 91}Rb and {sup 93}Rb. An analogous 27/2{sup -} state is expected to occur in {sup 95}Rb, as a long-lived isomer at 3.24 MeV. No such isomeric decay could be observed in a measurement using the Lohengrin spectrometer, which shows that, if it exists, its population, following the fission of {sup 235}U, is at least four times lower than that of the analogous 27/2{sup -} isomer in {sup 97}Y.