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Population of High-Spin Isomeric States Following Fragmentation of U-238

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Original languageEnglish
JournalPhysical Review C
Issue number2
Publication statusPublished - 16 Aug 2013


Isomeric ratios have been determined for 23 metastable states identified in A approximate to 200 nuclei from Pt to Rn near the valley of stability following fragmentation of U-238. This includes high-spin states with angular momenta ranging from (39/2)(h) over bar to 25 (h) over bar. The experimental results are discussed together with those of similar experiments performed in this mass region. Isomeric ratios are compared with theoretical predictions where the angular momentum of the fragment arises purely due to the angular momentum of nucleons removed from the projectile. The theoretical yield of low-spin states is generally overestimated. In these cases the assumption of 100% feeding of the isomer may require modification. However, the yield of high-spin isomeric states [I-m >= (39/2)(h) over bar] is significantly underestimated and highlights the requirement for a more complete theoretical framework in relation to the generation of fragment angular momentum. The enhanced population of high-spin states reported here is advantageous to future studies involving isomeric beams at fragmentation facilities such as the Rikagaku Kenkyusho RI Beam Factory (Japan) and next-generation facilities at the Facility for Antiproton and Ion Research (Germany) and Facility for Rare Isotope Beams (USA).

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