Nuclear structure study of the neutron deficient cadmium isotopes100, 101, 102Cd

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Abstract:The particles and two proton holes from l~176 is a good candidate for studying the two-particle(hole) valence configurations outside the doubly magic core and their mutual interaction. Excited states of l~176 were first identified in-beam by Alber et al. [1], and the 7-decay, half life and g-factor of the I~=(8 +) isomer were determined in two successive publications [2,3]. A shell model analysis of the existing data [3] revealed a predominant proton rgg/2 -2 configuration for the isomer and neutron nature for the lower spin states connected by the (8+)~(6 +) 4(4+)4(2+)--*0 + E2 cascade. Shell model predictions suggest, that the non-yrast I~=6 + and 4 + states are fed only by weak "f-ray branches, below the detection limits of previous experiments. "y-decay and half life of the tl/2=60(3) ns U=8 + isomer in l~176 Cd have been studied with a recoil catche~ setup inside the multidetector "y-array OSIRIS. Evaporation neutrons and charged particles from the reaction SSNi+ 46 Ti were measured in coincidence with delayed "g-rays. Six new "y-ray transitions with intensities of 1-10~o of the mainWe have therefore designed an experiment to exclusively study the isomeric decay. Excited evaporation residues recoiling from the reaction 46Ti (SSNi,2p2n) were stopped 40 cm downstream from the 1.5 mg/cm 2 thick target in 32 mg/cm 2 Nb foils. The energy of the beam from the tandem-cyclotron combination of VICKSI was 230 MeV. The catcher foils had an inner hole of 10 mm diameter for the beam and were located in the center of the OSIRIS 'y-array, which consists of 12 HPGe detectors in BGO Anti-Compton shields [4]. The detectors were positioned in two rings at 90+250 relative to the beam, and, in view of the low multiplicity of delayed 'y-rays, were used without collimators to suit the large source diameter of 8 cm. Filter detectors for neutrons (6 segments) [5] and charged particles (4 segments) [6] surrounded the target, as de-* Senior U.S. Scientist Humboldt Fellow on leave from SUNY, Stony Brook, N.Y., USA scribed elsewhere [7]. The catcher foils were exchanged every 2 hours to avoid excessive 'y-ray background from radioactivity. Further details are given in forthcoming papers [7,8]. Coincidences between evaporated neutrons, charged particles and single 7 and 77 events were stored event by event on exabyte tape, and sorted off-line into particle gated "/'7 and 'yt matrices with time measured relative to the cyclotron beam pulse.In Fig. 1, a sum coincidence spectrum with gates on neutrons and the 1005 keV 2+40 + and the 795 keV 4+42 + tran- Table 1. From 'y'y coincidences, intensities, cross-over transitions and energy sums the 'y-decay scheme of the I~=8 + isomer can be derived as shown in Fig. 2. As a first result the order of the 296 and 452 keV -/-rays in the E2 cascade, which could not be determined firmly in previous experiments [3], has to be reversed. With the now unique level sequence, the E2 character of the main cascade, as deduced from the anisotropies in a previous g-factor experiment [3], and the convers...

“…Further details of the shell model approach are given in Refs. [3,9]. The results are in good agreement with the experiment, considering that the reduced strengths in W.u.…”

supporting

confidence: 90%

mentioning

confidence: 53%

mentioning

confidence: 93%

mentioning

confidence: 99%

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The decay of theI ?=8+ isomer in100Cd-neutron particle and proton hole states

Górska

Schubart

Grawe

et al. 1994

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“…In the first approach (model A) aimed to describe nuclei with 42_<Z_<50 and 50_< N_< 57, a SSSr core was assumed, i.e. Further details on the SPE and the TBME values used will be given in forthcoming papers on 1~ [17], 1~176176176 [18], and ~~176 [19]. Neutrons were allowed in the ds/2, g7/2, Sxj2, and ds.,2 orbits.…”

Section: Shell Model Calculationsmentioning

confidence: 99%

Gamow-Teller beta decay of the very neutron-deficientN=50 nuclide98Cd

Płochocki

Rykaczewski

Batsch

et al. 1992

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For the first time, detailed decay-spectroscopic investigations were performed for the very neutron-deficient N=50 nuclide 9SCd. The 9SCd activity was produced in spallation reactions between 600 MeV protons and a natural tin target, yielding a 9SCd beam intensity of 10 to 60 atoms/s at the collector of the ISOLDE massseparator. By means of 7-ray and conversion-electron spectroscopy, 19 transitions were found to follow the /?+/EC decay 98Cd--*9SAg. The transitions at 61 and 107 keV were shown to be M 1(+ E 2) and E2, respectively, and the 98Cd half-life was measured as 9.2+0.3s. The QEC value of 9SCd is determined semiempirically and is compared to model predictions together with the measured QEc values of the neighbouring cadmium isotopes 1~176176 and the N=50 isotones 92M0, 94Ru, and 96pd, taken from the literature. The newly established decay scheme of 98Cd includes 9 excited states of 98Ag. Four states at 1691, 1861, 2164, and 2544 keV are directly fed by 0"~ 1 + Gamow-Teller beta transitions with a summed strength +0 s of 3.5-o17. This value corresponds to 25_+5% of the strength predicted for the GT transformation of a g9,2 proton (in 98Cd) into a g7/2 neutron (in 98Ag) by the extreme single-particle shell model. The GT-strength splitting and quenching, observed for 98Cd, are compared with the corresponding data for lighter even-even N = 50 isotones, and are discussed with reference to the predictions of more sophisticated nuclear models. We find that only in some cases it is possible to explain qualitatively the observed GT strength distribution and its total magnitude without renormalizing the free-neutron value of the axial-vector coupling constant.

Shell model structure at100Sn ? The nuclides98Ag,103In, and104, 105Sn

Schubart

Grawe²,

Heese³

et al. 1995

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The neutron deficient nuclei 9SAg, ~~ with Tz = 2 and 1~ l~ (Tz = 5/2) were studied in-beam following the reaction of 250 MeV 58Ni + 5~ Neutron and charged particle (p, 7) gated 77-coincidence spectra were used to identify these nuclei, which are populated with yields between 0.05% and 2% of the total residue cross section, and to determine their level schemes. In a comprehensive shell model study various approaches for the residual interaction were used to describe these newly and several previously studied neutron deficient nuclei. As a result predictions for the neutron single particle energies for ~~176 are obtained and used to discuss the next generation of experiments.