Study of superdeformed bands in nuclei withA ? 150 by heavy-ion-? coincidences

Recent data from the EUROGAM array have revealed the population of the yrast superdeformed (SD) band of lO2Hg in the ~n ezit channel of the 160 § reaction at 113 Me V beam energy. The nucleus assignment was made on the basis of the SD band transition en Re;~3.~0.Lv;27.80.+w Since the discovery of a discrete superdeformed (SD) band in 152Dy [1], many SD bands were found in the A~150 and A~190 regio~as~ but nearly all of them in the xn channels of heavy ion (HI) induced reactions. Very recently was reported the possibil~y to populate SD bands in a (HI,pxn) channel [2,3]. We report in this note on the first observation of a SD band populated in a (HI,ctxn) reaction channel. In order to study the SD band of 194pb [4], a highstatistic experiment has recently been performed using the 160+lS4w reaction at 113 MeV incident beam energy [5]. The oxygen beam was delivered by the Van de Graaftandem accelerator at the Nuclear Structure Facility, Daresbury Laboratory. The target consisted of two * Present address: CENBG, F-33170 Gradignan, France stacked 325 pg/cm 2 enriched lS4w foils, each deposited on 10/zg/cm 2 carbon backing. The "/-rays were detected with the phase 1 EUROGAM array, which consisted of 45 large volume Compton-suppressed germanium detectors [6]. Approximately 1.3 109 four-fold Comptonsuppressed events were collected. Within the experimentM conditions (at least 5 unsuppressed 7-rays detected in prompt coincidence), mainly three reaction exit channels were observed leading to loapb, 193pb, and 192Hg, with respective relative intensities of 605{, 13%, and 27%. The high yield of the ~4n channel offered the opportunity to check whether the SD band of 192Hg [7,8] was populated in such an exit channel. The main difficulty in this search is due to the fact that the SD yra~t bands in 192I-Ig and 194pb exhibit some 7-transitions very close in energy. Therefore, to reduce contamination from the 611 channel, triple-gated spectra were built. The background subtraction was performed using double-gated spectra. A selection of several combinations of gates on known SD lines in 192Hg were used, avoiding those contamined by the intense yrast lines (423 and 635 keV), and those close (less than 0.5 keV) to the 194pb SD lines (532.8 and 568.0 keV). The resulting spectrum is shown in fig. la. The same procedure was used to built a clean spectrum gated on 194pb SD lines ( fig.lb). Spectrum lb consists of the m4pb yra~t SD band, Pb X-rays (see insert), and low-lying 7-transitions of the normal level scheme of 194pb. Spectrum la exhibits a band with the same transition energies as those of the SD band of 192Hg, ranging from 214 up to 822 keV [8].

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Study of superdeformed bands in nuclei withA ? 150 by heavy-ion-? coincidences

Cited by 10 publications

References 22 publications

Electron Interactions with CF4, C2F6, and C3F8

Electron Interactions with CF4, C2F6, and C3F8

Density Functional Aspects of Relativistic Field Theories

First observation of a superdeformed nucleus produced in an α xn reaction channel

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