Yrast excitations around (sup 132)Sn: The two and three valence- proton N = 82 isotones (sup 134)Te and (sup 135)I

摘要

Large multidetector (gamma)-ray arrays, which can separate the prompt (gamma)-ray cascades within a single fission product nucleus (of moderate yield) from the bulk of prompt (gamma)-rays, has now opened new prospects for studies of yrast excitations in (sup 132)Sn and the few valence particle nuclei around it. Measurements were performed at Eurogam II using a (sup 248)Cm source. This paper features the results for the two and three valence proton N=82 isotones (sup 134)Te and (sup 135)I which exhibit simple clearcut excitation modes, resembling (sup 210)Po and (sup 211)At, their well studied N=126 counterparts in the (sup 208)Pb region. A search was made for new (sup 135)I transitions by setting a single coincidence gate on 1134 keV (gamma)-rays; strong 288, 572, 690, 725, 1661, 1695, and 2247 keV coincident (gamma)-rays were identified as (sup 135)I (gamma)-rays. In summary, yrast excitations to above 5.5 MeV excitation energy in the 2- and 3-proton nuclei (sup 134)Te and (sup 135)I have been established and interpreted with help of shell model calculations using empirical nucleon-nucleon interactions. This opens possibilities for exploring simple excitation modes in the (sup 132)Sn region under conditions comparable with but not identical to those in the well-studied (sup 208)Pb region.