The neutron deficient nucleus 96pd, four proton holes below the doubly magic l~176 has been studied in the reaction 64Zn (36Ar, 2p 2n). In n 7 and 77 coincidences levels up to 7 MeV excitation energy were established, and a new neutron core-excited isomer with 7"1/2=35(4)ns and g=0.83(5) was identified. A detailed shell model study yields excellent agreement for states within the 7r(p~/2, g9/2) configuration space but fails to reproduce the isomerism and g-factor for the core-excited state.
Excited states in 97Ag have been identified for the first time following the reactions 46Ti(SSNi, ep2n) and 64Zn(36Ar, p2n). The population cross sections were 1.0(5)mb and 0.7(3) rob, respectively. The y-decay of the seniority v = 3 states below the I~= (17/2-) and (21/2 +) isomers was investigated. In a search for short lived isomers half lives of t1/2=5(2 ) ns and 2.5(5)ns were found in the N=50 isotones 97Ag, U=(17/2-) and/or (21/2 +) and 95Rh, U=(21/2+). A new isomer was identified in 9Vpd, U=17/2 + with tl/2 = 2.3 (5) ns. The implication of the three-proton hole spectrum in ~~176 for the empirical residual interaction and shell model predictions is discussed.
The local susceptibilities and the 3d spin dynamics of isolated nickel ions in various alkali-metal hosts have been measured, utilizing the method of perturbed /-ray distribution after recoil implantation. In the heavy alkali-metal hosts Cs, Rb, and K, the local susceptibilities of the isolated Ni ions show the temperature behavior of a fully localized spin-orbit-coupled 3d 9 configuration. Clear host dependence of the magnetic behavior is seen in the spin-fluctuation rates which increase with decreasing host volume. In Na, the magnetic behavior drastically deviates from that of the purely ionic configuration, and Ni ions in Li as well as in Ca and Ba hosts are nonmagnetic.PACS numbers: 75.20.Hr, 75.30.Hx, 76.30.Fc, 76.80.+y In recent years the question of localization of electrons in the partially filled shells of transition metals has again become a subject of considerable interest. Following the table of transition elements by Smith and Kmetko, ! the degree of localization is the discriminating parameter for many bulk properties. The magnetism of most 4/ metals is known to be determined by localized electrons, whereas many d elements are strongly influenced by band structure and hybridization effects. Marking the change between localized and itinerant d and / electrons, the intermediate region, comprising, e.g., Ce and Fe, and Co and Ni, is rendered prominent by an extreme complexity of all-important bulk quantities.In the field of dilute magnetic alloys, the search for local moments is guided by the idea that magnetic moments will develop if the interaction of electrons "inside" one impurity atom survives hybridization or crystal fields. As nickel is estimated to have the strongest spinorbit coupling and exchange interaction in the 3d series, 2,3 a well-defined local magnetic moment might be expected in some metallic hosts, yet no such observation has been published.So the question arises whether nickel impurities will develop a fully localized configuration when incorporated in extreme environments. One such extreme system, which is characterized by sharp contrasts in atomic volume, electronegativity, and density of states between the constituents, has already been studied, Fe impurities in the alkali metals Cs, Rb, and K. 4 Here the isolated iron impurities are divalent and exhibit an unperturbed spin-orbit-coupled 3d 6 configuration. Another question of interest is the actual ionic configuration of the Ni ions in the host. Estimates on the basis of a Born-Haber cycle 5 suggest that Ni might be monovalent in the alkali metals and, even more interesting, might display charge fluctuations.In many metallic hosts Ni impurities show nonmagnetic behavior; in NiPd alloys, however, a positive magnetic hyperfine field has been found. 6 " 9 . This has been explained by negative core and positive orbital contributions and, in addition, transferred fields from neighbor-ing Pd atoms, but it is not an indication of an unperturbed well-defined moment. For Fe impurities, local orbital moments are thought to be typical f...
The very neutron deficient nucleus i~176 has been identified in the reaction 46Ti (58Ni, 2p2n) and its level scheme was studied up ~oEx = 4.3 MeV and I =12. A TI/2 = 40 10ns isomer was found at Ex=2.548 MeV with I~:(8+).Between the doubly magic shell closures at 4~ and 208pb the exotic "far-off-stability" nuclei close to lO~ are the only probes, accessible to in-beam spectroscopy, where a clear cut shell structure is expected and, hence, the residual nucleon-nucleon interaction can be studied. Shell model studies of less neutron deficient nuclei with N = 49 and N = 50 [I-3] have established a set of effective two-body matrix elements that account well for the proton structure of the N = 50 isotones in the upper g9/2 shell [4][5][6]. The strong proton-neutron interaction, which is responsible for the rapid evolution of deformation towards the Z-40, N = 40 and N = 60 regions, needs further investigation, since it fails to reproduce the spin gap isomerism in 95pd [7] and in the core excited 96 I00
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