Gamma-ray feeding and decay of superdeformed states

We report on four recent results concerning the population and the decay of superdeformed states, namely the structure of excited superdeformed states in ¹⁹⁴Hg, the search for fine structure of the last superdeformed transitions in ¹⁹⁴Pb, the primary decay-out strength analysis in ¹⁹⁴Hg and, as a consequence of this, the possibility of using the decay-out as a tool to study order-to-chaos properties of normally deformed states.Received: 3 December 2002, Published online: 17 February 2004PACS: 21.10.Re Collective levels - 23.20.Lv transitions and level energies - 24.60.-k Statistical theory and fluctuations - 24.60.Lz Chaos in nuclear systems - 27.80. + w F. Hannachi: Present address: CENBG/IN2P3, Gradignan, France.H. Amro: Present address: WNSL, Yale, USA.K. Hauschild: Present address: CSNSM/IN2P3, Orsay, France.T. Kröll: Present address: TU, Munich, Germany.M. Rejmund: Present address: GANIL, Caen, France.     

Evaluation of the echolocation model for range estimation of multiple closely spaced objects

Experimental evidence indicates that bats can use frequency-modulated echolocation to identify objects with an accuracy of less than 1 μs. However, when modeling this process, it is difficult to estimate the delay times of multiple closely spaced objects by analyzing the echo spectrum, because the sequence of delay separations cannot be determined without information on the temporal changes in the interference patterns of the echoes. To extract the temporal changes, Gaussian chirplets with a carrier frequency compatible with bat emission sweep rates are introduced. The delay time for object 1 (T(1)) is estimated from the echo spectrum around the onset time. The T(2) is obtained by adding the T(1) to the delay separation between objects 1 and 2. Further objects are located in sequence by this procedure. Here echoes were measured from single and multiple objects at a low signal-to-noise ratio. It was confirmed that the delay time for a single object could be estimated with an accuracy of about 1.3 μs. The range accuracy was less than 6 μs when the frequency bandwidth was less than 10 kHz. The delay time for multiple closely spaced objects could be estimated with a high range resolution by extracting the interference pattern.     

Holding characteristics of planar objects suspended by near-field acoustic levitation

The authors have found the acoustic levitation phenomenon where planar objects of 10 kg weight can be levitated near a vibration surface. This phenomenon has been studied for non-contact transportation. A circular planar object can be suspended without contacting a circular vibration plate. We have studied the holding force which acts horizontally on the levitated objects. The horizontal position of the object is stabilized by this force. In this paper, we discuss the effect of the radius of a levitated object, levitation distance, displacement amplitude of the vibration plate and the vibration mode on the suspending force.     

Molecular dynamics of [(CH2OH)3CNH3]2SiF6 by phase transition of 178 K

We have investigated the molecular motions of TRIS⁺ ([(CH₂OH)₃CNH₃]⁺) and ions in the [(CH₂OH)₃CNH₃]₂SiF₆ crystal below room temperature from the measurements of the spin-lattice relaxation time T₁ and the NMR absorption line of ¹H and ¹⁹F nuclei, in order to elucidate the changes of the molecular motions by the phase transition of T_c=178 K. The narrowing of the ¹⁹F-NMR line was observed around T_c=178 K and the reorientation of the anion appears above T_c. Moreover, from the analysis of the temperature dependence of T₁, we have observed that the activation energy of the reorientational motion of ions changes from 0.168 eV (T>T_c) to 0.185 eV (T<T_c). Based on these results, we found that the reorientational motion of ions is closely related to the origin of the phase transition at T_c. In addition, from the measurement of the ¹H-NMR line, we also found that the reorientational motion of H₂ in the -CH₂OH group becomes active accompanied by the phase transition.     

Calorimetric study of proton ordering in hexagonal ice catalyzed by hydrogen fluoride

Heat capacities of hexagonal ices doped with 2.6, 26 and 260 m mol dm^?3 HF were measured with an adiabatic calorimeter. The HF doping accelerated proton ordering which has been known to take place sluggishly around 100 K. The ice containing 26 m mol dm^?3 HF showed the largest excess entropy ((0.102±0.01) J K^?1 mol^?1) and the shortest relaxation time. The relaxation time at 90 K was about $\text{1}\text{30}$ of that of the pure ice I_h at the same temperature. The activation enthalpies obtained were the same for all of the doped ices, (23.5±2.0) J mol^?1, which is approximately equal to the activation energy of the mobility of the Bjerrum L-defect.     

Experimental realization of a spin-1/2 triangular-lattice Heisenberg antiferromagnet

We report the results of magnetization and specific heat measurements on Ba{3}CoSb{2}O{9}, in which the magnetic Co{2+} ion has a fictitious spin 1/2, and provide evidence that a spin-1/2 Heisenberg antiferromagnet on a regular triangular lattice is actually realized in Ba{3}CoSb{2}O{9}. We found that the entire magnetization curve including the one-third quantum magnetization plateau is in excellent quantitative agreement with the results of theoretical calculations. We also found that Ba{3}CoSb{2}O{9} undergoes a three-step transition within a narrow temperature range.     

Search for electric dipole moment in 129Xe atom using a nuclear spin oscillator

We aim to measure the electric dipole moment (EDM) of a diamagnetic atom ¹²⁹Xe using an optical-detection nuclear spin maser technique. The relation of EDM in a diamagnetic atom to nuclear Schiff moment and fundamental sources generating it is discussed, and the present status for the development of our experimental setup is presented.     

Volume-dependence of phonon frequencies and mode Grüneisen parameters for Si and Ge

The volume-dependence of phonon frequencies for Si and Ge is studied using higher-order perturbation and local Heine-Abarenkov model pseudopotential. The obtained mode Grüneisen parameters at atmospheric pressure are in good agreement with the experimental data. The mode Grüneisen parameters obtained for the Raman, TO, LO and LA modes increase slightly with decreasing volume. The other TA mode Grüneisen parameters decrease strongly as function of the volume strain, and give important contribution to the anharmonic properties of Si and Ge. The pressure dependence of phonon frequencies for Raman and some modes at the zone boundaries are estimated over the whole region of the compressed volume before the pressure induced covalent-metallic phase transition.     

Electrical characteristics of oxide-nitride-oxide films formed ontunnel-structured stacked capacitors

Current conduction mechanism of oxide-nitride-oxide films formed on tunnel-structured stacked capacitor (TSSC) was studied. At positive and negative bias, the Poole-Frenkel (P-F) conduction of holes in the nitride (SiN_x) film dominates the total leakage current. From the P-F plot, the relative dielectric constant of the SiN_x was calculated. The electric field inside the structure was also calculated by assuming the model that characterizes the electrode shape inside the tunnel. From the results, the reason why the reliability of the TSSC is not lowered in comparison with the conventional stacked capacitor is discussed     

Phase transition and freezing of ionic disorder in CsNO2 and TINO2 crystals2

The heat capacities of CsNO₂ and TlNO₂ have been measured in the temperature region between 13 and 350 K. The phase transitions of CsNO₂ and TlNO₂ were found at (209.16 ± 0.10)K and (282.4 ± 0.1)K. The enthalpy and entropy of the phase transition were (3.45 ± 0.20) kJ mol^?1 and (17.2 ± 1.0) JK^?1 mol^?1 for the former, and (6.44 ± 0.31) kJ mol^?1 and (23.8 ± 1.1) JK^?1 mol^?1 for the latter. The glass transitions were found around 42 K in CsNO₂ and around 60 K for TlNO₂, respectively. The corresponding dielectric relaxations were observed between 58 and 130 K for CsNO₂ in the frequency range between 10² and 10⁵ Hz and between 80 and 180 K for TlNO₂ in the frequency range between 2 × 10² and 10⁵ Hz. The calorimetric and dielectric relaxation times yielded a straight line in the Arrhenius plot over a wide time scale ranging from 10^?6 to 10⁵ sec. The slope gave the activation enthalpy of 13.8 kJ mol^?1 and 19.5 kJ mol^?1 for CsNO₂ and TlNO₂, respectively. The transition entropy supplemented by a residual entropy R ln 3 for CsNO₂ and R ln 2 for TlNO₂ gave (26.3 ± 1.0) JK^?1 mol^?1 and (29.6 ± 1.1) JK^?1 mol^?1 for the orientational entropy of the NO₂^? ion in the high-temperature phase. Based on the packing and symmetry considerations, these entropies were interpreted by the model which included two different sets of orientations of the NO₂^? ions parallel to [110] and [111] in the CsCl type unit cell. The existence of the different sets of orientation was proved by the doublet (Δv ~ 10 cm^?1) of the Raman spectrum of the bending mode of the NO₂^? ion in the cubic phase of the CsNO₂ crystal. The band narrowed to an ordinary singlet with increasing temperature. This observation was accounted for as the motional narrowing in which the NO₂^? ion felt an averaged field of the two different sets owing to the increased rate of jumping as the temperature increased.