The search for Hyperdeformation in152Dy

Three experiments have been carried out to search for the existence of Hyperdeformed states (HD) in the nucleus¹⁵²Dy. These three experiments were designed to test different properties of the expected HD structures. As a result of these experiments no clear evidence for HD states in¹⁵²Dy has been observed.     

γ-Rays draining the superdeformed band in152Dy

Further analysis of earlier¹⁵²Gd(α,4n) in-beam data revealed several previously unplaced¹⁵²Dy γ-rays feeding the oblate yrast states, among them γ-transitions emitted in decay of the superdeformed band. We can also weakly detect the lowest two members of the superdeformed cascade, but our data were not quite good enough to make a firm connection to them.     

Thex- (orΔ) transition in152Dy

A 53.3 keV E2 transition de-exciting the 60 ns isomer in¹⁵²Dy has been identified in γγ-coincidence measurements, which locates that isomer at E_x=5088 keV. The half life of the 11^? level at 3161 keV was measured to be T_1/2=4.3±0.9 ns.     

Interpretation of observed superdeformed and other collective bands in 152Dy

The shell effects responsible for superdeformation in the ¹⁵²Dy region are discussed. Why is only one band observed in ¹⁵²Dy and why is there another coexistent collective band? How does the superdeformed band decay?     

Electromagnetic properties of high spin states in158Dy and164Dy

We present calculations of electromagnetic properties of¹⁵⁸Dy and¹⁶⁴Dy based on the solution of the self-consistent cranking model and approximate angular momentum projection technique developed earlier. The calculated values compare fairly well with the existing experimental data.     

Particle-hole states at high spin in 150Dy

The level scheme of the nucleus ¹⁵⁰Dy up to spin around 40 was obtained using the reaction ¹¹⁴Cd(⁴⁰Ar, 4n). Above spins 20 to 22 — the highest obtainable from the valence nucleons — the breaking of the ¹⁴⁶Gd pproton and neutron cores occurs in separate parallel cascades.     

Single particle nature of the yrast line at high angular momentum in 152Dy

Linear polarization and Doppler shift recoil-distance decay curves for γ-ray transitions deexciting very high spin yrast states up to spin 36? in ¹⁵²Dy were measured with a delayed-promt γ-γ coincidence technique via the reactions ¹²²Sn (³⁴S, 4n) and ¹²⁴Sn(³²S, 4n), at 150 MeV incident beam energy. The deduced experimental transition probabilities are consistent with those obtained for non-rotational nuclei indicating that the yrast angular momentum originates mainly from the alignment of individual particle spins.     

High-spin states in neutron-rich Dy isotopes populated in deep-inelastic reactions

High-spin states in neutron-rich Dy isotopes, populated in deep-inelastic processes produced by the interaction of 234 MeV ³⁷Cl ions with a ¹⁶⁰Gd target, have been studied using the highly sensitive EUROBALL IV gamma-ray detector array. The previously known level schemes for ^{159,160,161,162}Dy have been extended to significantly higher spin ( ? 30?) and the i _13/2 band crossing in ¹⁵⁹Dy has been observed for the first time. The experimental results are discussed within the framework of cranked shell model and projected shell model calculations with particular reference to the observed delayed band crossing in ¹⁶²Dy. Received: 20 October 2000 / Accepted: 16 January 2001     

Synchronous states of slowly rotating pendula

Coupled systems that contain rotating elements are typical in physical, biological and engineering applications and for years have been the subject of intensive studies. One problem of scientific interest, which among others occurs in such systems is the phenomenon of synchronization of different rotating parts. Despite different initial conditions, after a sufficiently long transient, the rotating parts move in the same way — complete synchronization, or a permanent constant shift is established between their displacements, i.e., the angles of rotation — phase synchronization. Synchronization occurs due to dependence of the periods of rotating elements motion and the displacement of the base on which these elements are mounted.     

Gyromagnetic ratios of excited states in 150Sm and 152Sm

The gyromagnetic ratios of the 2₁⁺, 4₁⁺, 6₁⁺, 2₂⁺, and 2₃⁺ states in ¹⁵⁰Sm and the 2₁⁺, 4₁⁺, 6₁⁺, 8₁⁺, 10₁⁺, 2₂⁺, and 2₃⁺ levels in ¹⁵²Sm have been measured using the transient field perturbed γ-ray angular correlation technique. States of interest were populated by multiple Coulomb excitation using 150- and 220-MeV ⁵⁸Ni beams. The present results display no significant deviation from constancy of the g-factors of all levels investigated in either isotope separately or of corresponding states in ^150,152Sm. These findings are compared with available prior measurements and assessed in terms of applicable theoretical model calculations.     

Shape Transition and Triaxial Interaction Effect in the Structure of 152-166Dy Isotopes

The positive parity states in even-even ^152-166Dy are studied systematically in the framework of the interacting boson model (IBM). A cubic term, L=3, has been added to the Hamiltonian in order to produce the effect of triaxiality on the energy spectrum. The potential energy surfaces as a function of β and γ deformation parameters, for all isotopes have been produced. Energy levels and reduced electric quadrupole transition probabilities are calculated in framework of IBM with Cubic term (IBMC). All results are compared with available experimental data. It is found that these isotopes can be described by a schematic Hamiltonian in transition from U(5) (vibration) to SU(3) (rotation) dynamic symmetry.     

Description of low-lying vibrational and two-quasiparticle states in164Dy

The calculation with the deformed Woods-Saxon potential and residual interaction allowing for a twophonon admixture of the quadrupole, octupole and hexadecapole vibrational and two-quasiparticle states in¹⁶⁴Dy have been made. The calculated excitation energies and B(E; =2, 3, 4) values are found to be in reasonable agreement with experimental data. The calculated 0⁺ states in¹⁶⁸Er do not contradict experimental data. It is shown that the wave functions of states with energies below 2.3 MeV have dominating one-phonon components.     

Measurement of the g-Factor of the 27− High-Spin Isomer State of 152Dy

The g-factor of the 27⁻ isomer state of ¹⁵²Dy has been measured using the Time-Integral Perturbed Angular Distribution (TIPAD) method. The high-spin states of ¹⁵²Dy have been populated by ¹⁴¹Pr(¹⁶O,p4n)¹⁵²Dy reaction at E = 115 MeV from the AVF cyclotron at CYRIC. The paramagnetic correction factor of Dy ions in Pr has been determined to be 4.2(5) by the Time-Differential Perturbed Angular Distribution (TDPAD) measurement of the 21⁻ state of ¹⁵²Dy. As a result, the g-factor of the 27⁻ isomer state of ¹⁵²Dy has been obtained to be +0.09(5). This shows the smaller value than the expected one of +0.39 deduced from a fully aligned configuration of π(h _11/2 ²) ⊗ ν(f _7/2 ² h _9/2 i _13/2).     

Critical Point of the 152Sm, 154Gd,and 156Dy Isotones

Physics of Atomic Nuclei - The even—even rare-earth nuclei in U(5)—SU(3) region at neutron number (N) = 90, have been systematically studied using the Bohr—Mottelson Model (BM),...     

Beta-delayed gammas and QEC-values in the decays of150m,152mHo and149Dy

^{150m, 152m}Ho, and¹⁴⁹Dy were produced by fusion-evaporation reactions of⁴⁰Ar with targets of natural indium and¹¹⁴Cd. Theβ-decays of the isotopes were reinvestigated with emphasis on high-excitation daughter states. The decay energies for selectedβ-transitions were measured from electron-capture to positron-decay ratios. Corrections forγ-feeding from higher-lying states were taken into account. The following Q_EC-values were derived for^150mHo,^152mHo, and^149mDy of 6819 ( _?100 ⁺¹¹⁷ , 6263 ( _?80 ⁺⁸⁹ ), and 3914 ( _?52 ⁺⁷⁶ ) keV, respectively.