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Modelling crystal-field interaction for f-elements in LaCl{sub 3}

Description: The results of crystal field calculations in the framework of exchange charge model (ECM) are reported for trivalent lanthanide and actinide ions doped into LaCl{sub 3}. Whereas the scalar strength of the model crystal field parameters are consistent with that previously determined by fitting the experimental data, the sign of the second-order parameter is found to be negative, in contrast to previous reports. The contribution from long-range electrostatic interactions exceeds that from the nearest neighboring ligands and leads to the negative sign of the second-order crystal field parameter. Other interaction mechanisms including overlap, covalence, and charge exchange are less important to the second order parameter, but dominate the fourth-and sixth-order parameters. This work provides a consistent interpretation of the previously controversial experimental results for both lanthanide and actinide ions in this classical host.
Date: September 1, 1997
Creator: Zhorin, V.V. & Liu, G.K.
Partner: UNT Libraries Government Documents Department

Deformed proton emitters.

Description: The mechanisms of proton radioactivity from deformed rare earth nuclei are discussed and preliminary results on the fine structure decay of {sup 131}Eu are presented.
Date: February 17, 1999
Creator: Carpenter, M. P.; Cizewski, J. A.; Davids, C. N.; Davinson, T.; Fotiades, N.; Henderson, D. J. et al.
Partner: UNT Libraries Government Documents Department

Octupole effects in the lanthanides

Description: Arrays of Anti-Compton Spectrometer enabled systematic investigations of octupole correlations in the neutron-rich lanthanides. The studies mostly confirm the theoretical expectations of moderate octupole deformation at medium spins in nuclei from this region but in some cases predictions deviate from the experiment. In cesium isotopes strong octupole effects are predicted but not observed and new measurements for {sup 139}Xe suggest octupole effects stronger than expected. Systematics of excitation energy of the 31 states excitations, updated in the present work for Xe isotopes, indicates the N=85 and Z=54 lines as borders for strong octupole correlations. Systematic of electric dipole moment, upgraded in the present work for Ca and Ce isotopes confirms the Z=54 limit and adds new information about local canceling of electric dipole moment at the N=90 neutron number.
Date: October 22, 1999
Creator: Urban, W.; Rzaca-Urban, T.; Phillips, W. R.; Durell, J. L.; Leddy, M. J.; Smith, A. G. et al.
Partner: UNT Libraries Government Documents Department

Workshop on nuclear structure at moderate and high spin: Slide report

Description: The workshop was scheduled to coincide with the beginning of operation of a number of large arrays of Compton-suppressed germanium detectors. The workshop was divided into 14 sessions containing 3 presentations each. The topics of these sessions were superdeformation, heavy rare earths, single-particle configurations, band termination, continuum properties, light rare-earths, new techniques, high temperatures, transfer reactions, transition region, shapes, lifetimes, and moments. This publication consists of the slides used in all of the presentations at the workshop.
Date: October 1, 1986
Partner: UNT Libraries Government Documents Department

Nuclear states and shapes at high spin. [Good review]

Description: As angular momentum is added to a nucleus, the balance of forces acting upon it to determine its shape, moment of inertia, mode of rotation, and type of level structure may undergo a series of changes. At relatively low spins a deformed nucleus will rotate collectively, and one may see the effect of Coriolis antipairing in gradually increasing the moment of inertia. Around spin 12 to 16 h-bar there may be an abrupt change (backbending) when a pair of high-j nucleons unpairs and the nucleons align with the axis of rotation; this process allows the nucleus to slow its collective rotation. This process, the start of a sharing of angular momentum between single-particle motion and the collective rotation, gives a lower total energy and corresponds to a change toward triaxiality in the shape of the nucleus. At much higher spins discrete ..gamma..-ray transitions can no longer be observed. This is the regime of continuum spectra; all the information on these high-spin states (to 65 h-bar) is contained in these continuum cascades. Knowledge is accumulating on how to study these spectra, experimentally and theoretically, and new techniques offer promise of revealing a great deal of information about the shapes and properties of very high spin states. 71 references, 34 figures.
Date: August 1, 1980
Creator: Diamond, R.M.
Partner: UNT Libraries Government Documents Department

M1 transitions between collective levels and F-spin purity

Description: M1 transitions between low-lying collective levels in deformed nuclei are described within the IBM-2 framework. This is done by a special choice of the Hamiltonian which allows a simultaneous fit of energies, E2 and M1 transitions. Finally, the results are interpreted using the F-spin concept. 12 refs., 4 tabs.
Date: January 1, 1987
Creator: von Brentano, P.; Frank, W.; Gelberg, A.; Harter, H.; Krips, W.; Casten, R.F. et al.
Partner: UNT Libraries Government Documents Department

Microscopic analysis of angular momentum projected HFB-states in terms of interacting bosons

Description: Angular momentum- and number-projected Hartree-Fock-Bogoliubov (HFB) wavefunctions for transitional and deformed Rare Earth nuclei are analyzed in terms of Fermion pairs coupled to angular momenta L = 0(S), 2(D), 4(G), ... The Fermion space is truncated to contain only S-D or S-D-G pairs. The variation is carried out before and after angular momentum projection and with different truncations. The influence of the truncation on physical quantities such as moments of inertia, quadrupole moments or pair transfer matrix elements is discussed. 21 references.
Date: December 1, 1984
Creator: Ring, P. & Pannert, W.
Partner: UNT Libraries Government Documents Department

E4 moments for deformed rare-earth and heavy transitional nuclei

Description: Techniques for measuring reduced matrix elements <4/sup +/ parallel M(E4) parallel 0/sup +/>, the interpretation of these data, and the implications for various nuclear models are reviewed and discussed. Actual examples are confined to deformed rare-earth and heavy transitional nuclei. 33 refs., 9 figs.
Date: August 1, 1987
Creator: Baker, F.T.
Partner: UNT Libraries Government Documents Department

Heavy-ion-induced fission in the rare-earth region and the statistical model

Description: Two separate aspects of heavy-ion-induced fission in the rare-earth region are considered. First, fission excitation functions and their relationship to fission barriers are considered. Second, results on neutron emission associated with fission are briefly discussed in the context of the statistical deexcitation model.
Date: January 1, 1982
Creator: Plasil, F.; Beene, J.R.; Cheynis, B.; Ferguson, R.L.; Obenshain, F.E.; Sierk, A.J. et al.
Partner: UNT Libraries Government Documents Department

Nuclear-decay studies of neutron-rich rare-earth nuclides

Description: Neutron-rich rare-earth nuclei were produced in multinucleon transfer reactions of {sup 170}Er and {sup 176}Yb projectiles on {sup nat}W targets at the Lawrence Berkeley Laboratory SuperHILAC and their radioactive decays properties studied at the on-line mass separation facility OASIS. Two unknown isotopes, {sup 169}Dy (t {sub 1/2} {equals} 39 {plus minus} 8 s) and {sup 174}Er(t{sub 1/2} {equals} 3.3 {plus minus} 0.2 m) were discovered and their decay characteristics determined. The decay schemes for two previously identified isotopes, {sup 168}Dy (t{sub 1/2} {equals} 8.8 {plus minus} 0.3 m) and {sup 171}Ho (t{sub 1/2} {equals} 55 {plus minus} 3 s), were characterized. Evidence for a new isomer of 3.0 m {sup 168}Ho{sup g}, {sup 168}Ho{sup m} (t{sub 1/2} {equals} 132 {plus minus} 4 s) which decays by isomeric transition (IT) is presented. Beta particle endpoint energies were determined for the decay of {sup 168}Ho{sup g}, {sup 169}Dy, {sup 171}Ho, and {sup 174}Er, the resulting Q{beta}-values are: 2.93 {plus minus} 0.03, 3.2 {plus minus} 0.3, 3.2 {plus minus} 0.6, and 1.8 {plus minus} 0.2 MeV, respectively. These values were compared with values calculated using recent atomic mass formulae. Comparisons of various target/ion source geometries used in the OASIS mass separator facility for these multinucleon transfer reactions were performed. 73 refs., 40 figs., 11 tabs.
Date: April 26, 1990
Creator: Chasteler, R.M. (California Univ., Berkeley, CA (USA). Dept. of Chemistry Lawrence Berkeley Lab., CA (USA))
Partner: UNT Libraries Government Documents Department

Studies of yrast and continuum states in A=140-160 nuclei. Progress report, January 1, 1980-December 31, 1980. [Purdue Univ. , 1/1/80-12/31/80]

Description: The structure of nuclei in the A approx. 150 region was investigated by in-beam ..gamma..-ray spectroscopy using heavy-ion beams, mostly from the Argonne Tandem-Linac. Results for the nuclei /sup 148/Dy, /sup 149/Dy, /sup 153/Dy, /sup 154/Dy, /sup 149/Ho, and /sup 150/Ho are summarized. The feeding of yrast states in these nuclei and the link between the highest known yrast states and the continuum region were also studied. 6 figures.
Date: January 1, 1981
Creator: Daly, P.J.
Partner: UNT Libraries Government Documents Department

Magnetic hyperfine fields in Dy/sub 1-x/Y/sub x/Al/sub 2/

Description: /sup 161/Dy Moessbauer spectroscopy was carried out at 4.2 K on Dy/sub 1-x/Y/sub x/Al/sub 2/ for 0 less than or equal to x less than or equal to 0.6. For x=0 we find B=580 T and f/sub Q/=2810 MHz, close to free-ion values. For x > 0 both B and f/sub Q/ decrease weakly. We obtain (..delta..B)/sub n/ = -14 T, (..delta..f/sub Q/)/sub n/ = -110 MHz and (..delta..B)/sub nn/ = + 1.6 T, (..delta..f/sub Q/)/sub nn/ = +4 MHz per replaced nearest and next-nearest Dy/sup 3 +/ neighbor, respectively.
Date: January 1, 1982
Creator: Hessel, A.; Kalvius, G.M.; Shenoy, G.K.; Zinn, W. & Wiedemann, W.
Partner: UNT Libraries Government Documents Department

Moessbauer studies of dilute erbium impurities in zirconium hydrides

Description: Hyperfine spectra are reported for Er present as a dilute impurity in the fluorite structure compound delta-ZrH/sub 1/ /sub 5/ and the tetragonally distorted fluorite epsilon-ZrH/sub 1/ /sub 87/. In both cases, the hyperfine spectra are identical and show cubic symmetry around the Er ion regardless of the host crystal structure, showing the formation of a locally cubic Er-hydrogen cluster. Paramagnetic relaxation frequencies are also identical in the two phases, in spite of large changes in the electronic density of states. Mechanisms for the formation of such Er-hydrogen clusters are discussed.
Date: January 1, 1978
Creator: Shenoy, G.K.; Dunlap, B.D. & Westlake, D.G.
Partner: UNT Libraries Government Documents Department

Understanding nuclear quadrupole deformations

Description: A simple ansatz that ''Nuclei, not too near closed shells, are as deformed as they can be within a single major shell'' appears to quantitatively reproduce the variations of the quadrupole moments and hence the deformations of nuclei. 6 refs., 3 figs.
Date: January 1, 1989
Creator: Raman, S.
Partner: UNT Libraries Government Documents Department

Use of high-pressure ion exchange for the production of gadolinium-153. Status report

Description: A large high-pressure ion-exchange column, which had been designed for the separation of gadolinium from europium, was tested in the laboratory. Good separations were obtained. Subsequently, columns of the same design were installed in a hot cell and have been used successfully for the separation of gadolinium-153 from irradiated natural europium. The gadolinium-153 production achieved using these columns is substantially greater than that achieved using the previous process. Rapid damage of the resin is a problem and frequent resin changes are required.
Date: April 1, 1986
Creator: Posey, J.C.
Partner: UNT Libraries Government Documents Department

Empirical estimates of the proton-neutron interaction and diabolical points

Description: The use of constant-N contours in the ({omega},{lambda}) plane is demonstrated both for establishing diabolical points and for studying regularities and fluctuations in the spectrum of single-particle states. Likewise the average properties and fluctuations of empirical proton-neutron interactions, obtained from double differentials of the total energy with respect to N and Z, are discussed for the ground states of all even-even nuclei with N > 40 and as a function of the rotational frequency for the lowest even-spin, positive-parity decay sequence of deformed rare earth nuclei. 25 refs., 3 figs.
Date: January 1, 1990
Creator: Zhang, J.-Y. (Academia Sinica, Beijing, BJ (China). Inst. of Theoretical Physics Brookhaven National Lab., Upton, NY (USA) Joint Inst. for Heavy Ion Research, Oak Ridge, TN (USA) Academia Sinica, Lanzhou, GS (China). Inst. of Modern Physics); Garrett, J.D. (Oak Ridge National Lab., TN (USA)); Casten, R.F. (Brookhaven National Lab., Upton, NY (USA)) & Brenner, D.S. (Clark Univ., Worcester, MA (USA)
Partner: UNT Libraries Government Documents Department

High spin isomers in /sup 153/Er

Description: Energy levels of /sup 153/Er were investigated with four NaI detectors in coincidence with a Ge(Li) detector. The existence of two long-lived high-spin isomers was confirmed, and their positions and decays were established. 1 figure. (RWR)
Date: January 1, 1980
Creator: Horn, D; Young, G R; Lister, C J & Baktash, C
Partner: UNT Libraries Government Documents Department

Novel, convenient, and nonpersistent radiotracer for environmental and energy applications

Description: A newly-available radioisotopic system, /sup 172/Hf-/sup 172/Lu, has excellent potential for tracer applications in which nuclear data acquisition must be accomplished in real time. The 6.7-day half-life of /sup 172/Lu is sufficient for a large fraction of tracer experiments, and should allow the direct incorporation of /sup 172/Lu into tests that have traditionally utilized much longer-lived radionuclides. Since /sup 172/Lu is the daughter component of a radioisotope generator, however, its effective shelf-life is determined by the half-life of its 1.9-year /sup 172/Hf parent. Consequently, the frequency of isotope procurement need not be any more extensive than investigators would normally be accustomed to. Discussion relevant to isotope production, generator operation, and nuclide acquisition is presented in this paper.
Date: March 12, 1984
Creator: Grant, P.M.
Partner: UNT Libraries Government Documents Department

Isotope shift in /sup 151,153/Eu/sup +/ from high-precision hyperfine structure measurements

Description: Isotope shift in the two stable isotopes of Eu/sup +/ has been obtained for four optical transitions between the states 4f/sup 7/(/sup 8/S/sup 0/)5d /sup 9/D/sub J//sup 0/ and 4f/sup 7/(/sup 8/S/sub 7/2//sup 0/)6p/sub 3/2/;J' using high-precision hyperfine structure measurements in a collinear laser and slow ion beam (1.35 keV) apparatus. 5 refs., 2 figs., 1 tab.
Date: January 1, 1987
Creator: Sen, A. & Childs, W.J.
Partner: UNT Libraries Government Documents Department

Phenomena at very high spins. [Approx. 70 h-bar; review]

Description: The present talk has three parts: first, a discussion of current ideas about the physics of very high spin states; second, some comments about noncollective behavior up to the highest spins where it is known, approx. 40 h; and finally, a presentation of the newest method for studying collective behavior up to spins of 60 to 70 h. The intention is that the overview presented in the first part will be sufficiently broad to indicate the relationship of the noncollective and collective behavior discussed in the other parts, and to provide some understanding of the compromise in behavior that seems to occur at the very highest spins. 13 figures.
Date: March 1, 1980
Creator: Stephens, F.S.
Partner: UNT Libraries Government Documents Department

Moessbauer effect of europium metal under pressure

Description: The pressure dependence of the magnetic hyperfine field and of the isomer shift of /sup 151/Eu in europium metal has been studied in a diamond anvil pressure cell at low temperatures. In the pressure range 0-12 GPa at 44/sup 0/K (T/sub N/ = 90/sup 0/K), the magnetic hyperfine field changes from -22 T to -8 T while the isomer shift increases from -7.3 to -3.8 mm s/sup -1/ relative to a SmF/sub 3/ source. The changes are interpreted as indicative of a pressure-driven intermediate valence state causing a reduced magnetic moment in Eu. Intermediate valence and magnetic order coexist over the range of pressures studied.
Date: September 1, 1986
Creator: Taylor, R.D. & Farrell, J.N.
Partner: UNT Libraries Government Documents Department

Development of optically pumped polarized jet targets for use in heavy-ion reaction studies

Description: The development of a laser optically pumped nuclear spin aligned target of /sup 151/ /sup 153/Eu is outlined. The current status of this project, together with the unique macroscopic heavy-ion reaction physics may be addressed using this target, is given. 14 references.
Date: January 1, 1984
Creator: Bemis, C.E. Jr.; Beene, J.R..; Ford, J.L.C. Jr.; Shapira, D. & Shivakumar, B.
Partner: UNT Libraries Government Documents Department