Results 1 - 10 of 2405
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[en] The Ehrenfest theorem and the explicit form of basic quantum operators defined in the Fock-Bargmann space are used to derive classical equations for the dynamics of the breathing mode of magic nuclei. Solutions to these equations are discussed for finite trajectories that satisfy the Bohr-Sommerfeld conditions. 11 refs., 1 tab
[en] This note will tabulate the desired phase and delay offsets for a Stacktail Momentum beam transfer function measurement as a function of beam energy and pickup leg. These phase and delay offsets were computed from beam transfer functions made around April 14, 2000. The StackTail system with these offsets will have a gain slope of about 10 MeV.
[en] Au25(SR)18- belongs to a new type of superatom that features an icosahedral Au13 core-shell structure and a protective layer of six RS(Au-SR)2 motifs. This superatom has a magic number of 8 free electrons that fully fill the 1s and 1p levels of the electron-shell model. By applying this superatom concept to the core-substitution chemistry of Au25(SR)18-, we first scanned the periodic table for the potential core atom M by applying a simple rule derived from the 8-electron count and then optimized the selected candidates by density functional theory calculations to create many series of M(at)Au24(SR)18q core-shell nanoclusters. We found that 16 elements from groups 1, 2, and 10-14 of the periodic table can maintain both electronic and geometric structures of the original Au25(SR)18- magic cluster, indicating that the electron-counting rule based on the superatom concept is powerful in predicting viable M(at)Au24(SR)18q clusters. Our work opens up a promising area for experimental exploration
[en] Atomic nuclei are classified according to the number of protons and neutrons they contain. Most of the 7000 or so nuclides that are possible are highly unstable, and many are only now being studied for the first time. On the other hand, it has been known for many years that nuclides containing ''magic'' numbers (2, 8, 20, 28, 50, 82 and 126) of protons or neutrons are unusually stable. However, three international teams of nuclear physicists have recently found new exceptions to this rule. They have shown that the old magic numbers disappear, and new ones appear, in certain exotic nuclei. In this article the author discusses these new results. (UK)
[en] Two different modes of the multibody collinear decay from the reaction "2"3"8U + "4He (40MeV) are discussed. Basing on the masses of three detected fragments one can come to conclusion that the decaying system in each mode looks like a chain consisting of two or three magic clusters respectively. Some of the clusters involved undergo 'second' clusterisation in the scission point leading to formation of dinuclear molecules. These latter can disintegrate via inelastic scattering on the materials on the flight path. (author)
[en] The superatom concept of metallic cluster valence is based on the electron-shell model as first proposed to explain the special stability of certain metal-atom clusters generated in the gas phase. It accounts for the magic-number series 2, 8, 18, 34, 58,... by shell-closing of the superatom orbitals 1S, 1P, 1D,.... Recently, the superatom-complex concept has been introduced to explain the compositions of high-yield gold-cluster compounds, especially Au25(SR)18- and Au102(SR)44 (with -SR being a thiolate group), corresponding to the magic numbers of 8 and 58, respectively. Surprisingly, no thiolated gold cluster accounting for the first closing (electron count 2) has yet been determined. Structure-bonding considerations lead us to propose Au12(SR)9+ as the superior candidate for the smallest thiolated gold superatom. This cluster features an octahedron core covered by three RS(AuSR)2 motifs. It has a unique C3 axis, is chiral, and possesses ideal aurophilic interactions and, therefore, should exist in nature. The folding of thiol-rich biomolecules may help us to realize this complex, which may also be prepared from available phosphine-ligated gold clusters.
[en] A method for the determination of different ''bare'' characteristics of the one-particle motion and one-particle basis in magic nuclei is described. The method is based on separating out the mixing with phonons from the phenomenological one-particle characteristics. By means of a generalization of the procedure for localization of the mass operator, relations linking the bare and phenomenological characteristics are obtained. The radial dependence of these characteristics in finite nuclei and the influence of the quasiparticle--phonon interaction on the phenomenological characteristics are studied. Calculations are performed for the neutrons in 208Pb