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

Abstract

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...

Observation of a core-excitedE4isomer inCd98

“…The background subtraction and the fitting procedure were optimized analyzing the decay of the I =8 + isomer in 100 Cd, which yielded a half-life value of T 1/2 =61͑1͒ ns in good agreement with Ref. [25]. Figure 4 shows the background subtracted time-delay spectrum with reference to the beam pulse on target for the new 4207 keV ␥ ray, which precedes the known I = ͑8 + ͒ isomer.…”

Shell-model-based deformation analysis of light cadmium isotopes

“…Since the proportionality factors in (10) are independent of µ, the tensor β sµ follows the same relations as Q sµ in equations (6) and (7) and thus it is sufficient to focus on the magnitude of the deformation β s instead of β sµ . The remaining difficulty now is to calculate the monopole moment r 2 .…”

C4898d50: The Two-Proton-Hole Spectrum inGórska1, Lipoglavšek2, Grawe3 et al. 1997Phys. Rev. Lett.Self Cite

“…This uncertainty of 25%, as a conservative estimate of systematic errors, is included in the 98 Cd value. From a comparison of the gg coincidence intensities to the well known 100 Cd nucleus [5,22], which was strongly populated in the present experiment, the production cross section was determined to be 20͑10͒ mb. Intensities were corrected for g-ray and particle detection efficiencies, assuming that in 98 Cd 100% of the g-ray flux is following the isomeric path.…”