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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

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

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

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

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

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

Investigation of nuclei near N = 82 and Z = 64 VIA radioactive decay of high-spin isomers

Description: An island of very high spin isomers was found recently in neutron-deficient Gd-Lu nuclei near the N = 82 closed shell in (H.I.,xn) measurements. This exciting discovery has led to a large number of experiments trying to identify the structures of these isomers and the nuclei in which they occur. These attempts have been helped in many instances by available spectroscopic information at low excitation energies. A systematic investigation of the low-lying structure of nuclei near N = 82 and Z greater than or equal to 64 was carried out. Heavy-ion beams were used to produce proton-rich isotopes which were then transported, with the use of gas-jet systems, to shielded areas where singles and coincidence ..gamma..-ray measurements could be made. Earlier investigations dealt with the decay of terbium (/sup 146 -149/Tb) and dysprosium (/sup 147 -152/Dy) nuclei. During the past two years the research program was extended to holmium nuclides (A less than or equal to 152) produced in /sup 10/B bombardments of samarium. Two new isotopes, /sup 149/Ho and /sup 148/Ho, were identified. The decay data of 21-s /sup 149/Ho supplement in-beam results and locate the hg//sub 2/ neutron state in /sup 149/ Dy to be at 1091 keV. The most intense ..gamma..-ray associated with 9-s /sup 148/Ho has an energy of 1688 keV. It is possibly the first-excited to ground-state transition in /sup 148/Dy. Recent in-beam measurements have shown that the first-excited state in /sup 146/Gd is, unespectedly, 3/sup -/ in contrast to doubly evenN = 82 nuclei below gadolinium where it is 2/sup +/. It would be interesting to determine whether the 1688-keV level in /sup 148/Dy, the next nucleus in this isotonic series, is 2reverse arrow or 3/sup -/ in character. 12 references.
Date: January 1, 1979
Creator: Toth, K.S.
Partner: UNT Libraries Government Documents Department

Measurement of atomic oscillator strengths in ytterbium by observation of coherent Rabi oscillations of excited-state populations

Description: Two methods have been used to measure the oscillator strength of the transition between the ground and 17,992 cm level in XUYb. The first technique involves exciting the transition with a laser pulse that is nearly time-bandwidth limited, of uniform intensity, and has a reproducible shape from shot to shot. The population left in the excited state after the pulse varies sinusoidally with a period that depends on the integral over time of the electric field amplitude and the transition oscillator strength. These are the Rabi oscillations that are predicted by application of the Schrodinger equation to the two-level atom. The second method involves observation of the polarization rotation of a set of degenerate sublevels brought about by a light-shift laser. One sublevel (m/sub j/ = 0) of the J = 1 level at 17,992 cm is populated by a linearly polarized laser. A second copropagating light-shift laser, which is linearly polarized at an angle to the first laser, is tuned between 7.5 and 30 GHz off-resonance with the transition. The light-shift laser causes population to be promoted into the m/sub j/ = +-1 levels through the virtual J = 0, m/sub j/ = 0 level. Two linearly polarized photoionizing lasers photoionize the population only from the m/sub j/ = +-1 levels. The photoion signal oscillates cosinusoidally with a period that depends only on the integrated pulse intensity, the laser detuning, and the transition oscillator strength. Finally, polarization selectivity has been shown experimentally to allow selective photoionization of the odd isotopes of ytterbium using broadband lasers.
Date: January 1, 1987
Creator: Haynam, C.A.; Comaskey, B.J.; Worden, E.F. & Paisner, J.A.
Partner: UNT Libraries Government Documents Department

M1-E2 mixing ratios of gamma-ground transitions in /sup 168/Er

Description: The L subshell ratios of four ..gamma..-g transitions in /sup 168/Er have been measured with the high resolution, iron, ..beta..-spectrometer at the Institut Laue-Langevin. The reduced M1-E2 mixing ratios are not consistent with the values predicted by Warner on the basis of IBA-1. It may be possible to explain the results in IBA-2 in terms of the ..delta..K = 1 mixing of the gamma-band and the pure antisymmetric states such as the 1+ isovector mode.
Date: September 10, 1984
Creator: Gelletly, W.; Warner, D.D.; Colvin, G.C. & Schreckenbach, K.
Partner: UNT Libraries Government Documents Department

Unexpected structure in the E2 quasicontinuum spectrum of /sup 154/Dy

Description: The evolution of the ..gamma.. quasicontinuum spectrum with neutron number has been investigated in the sequence of dysprosium isotopes /sup 152,154,156/Dy. The three nuclei display a pronounced collective E2 component. In /sup 154/Dy this component shows an unexpected splitting into two distinct parts, signifying a structural change along the ..gamma.. cascade. The E2 and statistical components can be reproduced in simple ..gamma.. cascade calculations; in /sup 152/Dy and /sup 156/Dy only rotational bands were included, whereas in /sup 154/Dy additional vibration-like transitions were required to reproduce the two E2 peaks. 11 refs., 2 figs.
Date: January 1, 1988
Creator: Holzmann, R.; Khoo, T.L.; Ma, W.C.; Ahmad, I.; Dichter, B.K.; Emling, H. et al.
Partner: UNT Libraries Government Documents Department