Status of vibrational structure in Ni62

Measurements consisting of γ-ray excitation functions and angular distributions were performed using the (n,n′γ) reaction on Ni62. The excitation function data allowed us to check the consistency of the placement of transitions in the level scheme. From γ-ray angular distributions, the lifetimes of levels up to ~3.8 MeV in excitation energy were extracted with the Doppler-shift attenuation method. The experimentally deduced values of reduced transition probabilities were compared with the predictions of the quadrupole vibrator model and with large-scale shell model calculations in the fp shell configuration space. Two-phonon states were found to exist with some notable deviation from the predictions of the quadrupole vibrator model, but no evidence for the existence of three-phonon states could be established. Z=28 proton core excitations played a major role in understanding the observed structure. © 2011 American Physical Society.

Thermodynamic formulation of flowing soft matter with transient forces

The Responsive Particle Dynamics model is a very efficient method to account for the transient forces present in complex fluids, such as solutions of entangled polymers. This coarse-grained model considers a solution of particles that are made of a core and a corona. The cores typically interact through conservative interactions, while the coronae transiently penetrate each other to form short-lived temporary interactions, typically of entropic origin. In this study, we reformulate the resulting rheological model within the general framework of nonequilibrium thermodynamics called General Equation for the Nonequilibrium Reversible-Irreversible Coupling. This allows us to determine the consistency of the model, from a mechanistic and thermodynamic point of view, and to isolate the reversible and irreversible contributions to the dynamics of the model system. © 2012 Springer-Verlag Berlin Heidelberg.

Modelling and design of stress-induced martensite formation in metastable β Ti alloys

The temperature dependence of the stress-induced martensite (SIM) formation in a Ti-10V-2Fe-3Al (Ti-1023) alloy under compressive loading has been studied. At low temperatures, the stress level at which martensite starts to form increases linearly with the deformation temperature, while the stress at which the deformation switches to regular plastic deformation is roughly temperature independent. A thermostatistical model for dislocation evolution is employed to describe deformation twinning in martensite. Combined effects of twinning induced plasticity and solid solution strengthening are considered in terms of temperature variations. The SIM effect disappears on deformation at temperatures beyond ~ 233 ° C, which is close to the predicted Ms temperature of 240°C. The thermostatistical model predicts a transition from twinned martensite to pure slip at 250°C. By providing a model to predict the martensite formation, and by describing deformation twinning, the present work provides a number of tools that may be employed to conceive new titanium alloys combining improved strength and ductility. © 2013 Elsevier B.V.

Microstructure of a-SiOx : H

A set of a-SiOx:H (0.52 < x < 1.58) films are fabricated by plasma-enhanced-chemical-vapor-deposition (PECVD) method at the substrate temperature of 250degreesC. The microstructure and local bonding configurations of the films are investigated in detail using micro-Raman scattering, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). It is found that the films are structural inhomogeneous, with five phases of Si, Si2O:H, SiO:H, Si2O3:H and SiO2 that coexist. The phase of Si is composed of nonhydrogenated amorphous silicon (a-Si) clusters that are spatially isolated. The average size of the clusters decreases with the increasing oxygen concentration x in the films. The results indicate that the structure of the present films can be described by a multi-shell model, which suggests that a-Si cluster is surrounded in turn by the subshells Of Si2O:H, SiO:H, Si2O3:H, and SiO2.

The microstructure and its high-temperature annealing behaviours of a-Si : O : H film

The microstructure and its annealing behaviours of a-Si:O:H film prepared by PECVD are investigated in detail using micro-Raman spectroscopy, X-ray photoelectron spectroscopy and Infrared absorption spectroscopy. The results indicate that the as-deposited a-Si:O:H film is structural inhomogeneous, with Si-riched phases surrounded by O-riched phases. The Si-riched phases are found to be nonhydrogenated amorphous silicon (a-Si) clusters, and the O-riched phases SiOx:H (x approximate to 1. 35) are formed by random bonding of Si, O and H atoms. By high-temperature annealing at 1150 degreesC, the SiOx:H (x approximate to 1.35) matrix is shown to be transformed into SiO2 and SiOx ( x approximate to 0.64), during which all of the hydrogen atoms in the film escape and some of silicon atoms are separated from the SiOx:H ( x approximate to 1.35) matrix; The separated silicon atoms are found to be participated in the nucleation and growth processes of solid-phase crystallization of the a-Si clusters, nano-crystalline silicon (ne-Si) is then formed. The microstructure of the annealed film is thereby described with a multi-shell model, in which the ne-Si clusters are embedded in SiOx (x = 0.64) and SiO2. The former is located at the boundaries of the nc-Si clusters, with a thickness comparable with the scale of nc-Si clusters, and forms the transition oxide layer between the ne-Si and the SiO2 matrix.

Raman scattering and infrared absorption of silicon nanocrystals in silicon oxide matrix

Structural dependence on annealing of a-SiOx:H was studied by using infrared absorption and Raman scattering. The appearance of Raman peaks in the range of 513-519cm(-1) after 1170 degreesC annealing was interpreted as the formation nanocrystalline silicon with the sizes from 3-10nm. The Raman spectra also show the existence of amorphous-like silicon phase, which is associated with Si-Si bond re-construction at boundaries of silicon nanocrystallites. The presence of the shoulder at 980cm(-1) of Si-O-Si stretching vibration at 1085cm(-1) in infrared spectra imply that except that SiO2 phase, there is silicon sub-oxide phase in the films annealed at 1170 degreesC. This sub-oxide phase is located at the interface between Si crystallites and SiO2, and thus support the shell model for the mixed structures of Si grains and SiO2 matrix.

Study of the νi13/2－1 band in 189Pt

High-spin levels of 189Pt have been studied with the in-beam γ-spectroscopy method via the 176Yb(18O,5n) reaction at the beam energies of 88 and 95 MeV. The previously known νi-131/2 band has been confirmed, and its unfavored signature branch extended up to the 13/2+ state. Within the framework of the triaxial particle-rotor model, the νi-113/2 band is suggested to be associated with the 11/2[615] configuration, and to have triaxial deformation.

Properties of the rotational bands in the transitional nucleus 189Pt

High-spin states in 189Pt have been studied experimentally using the 176Yb(18O,5n) reaction at beam energies of 88 and 95 MeV. The level scheme of189Pt has been revised significantly and extended to high-spin states.Rotational bands have been analyzed in the framework of triaxial particle-rotor model, and a γ ≈−30◦triaxial shape and a near-prolate shape have been proposed to the νi−113/2 and νf5/2(p3/2) bands, respectively. Two ΔI = 2 transition sequences with similar energies have been observed, and they have been proposed to be associated with the νi−213/2νf5/2(p3/2) configuration. The structure built on the νi−213/2νf5/2(p3/2) configuration could be interpreted theoretical calculations of the triaxial particle-rotor model if a near-oblate shape is assumed.

~(169)Re的转动带结构组态相关性研究(英文)

研究了~(169)Re的高自旋态能级结构,建立了组态为π9/2~-[514]的强耦合带和组态为π1/2~-[541]的退耦合带,推转壳模型(Cranked shell model)计算结果表明组态相关的不同形变能够解释这些转动带的不同带交叉频率,在已知的奇ARe核中,~(169)Re的9/2~-[514]转动带在低自旋时具有最大的能量旋称劈裂,当一对i_(13/2)中子顺排后,旋称劈裂发生了反转,并且劈裂的幅度非常显著地减少了,另外,还观测到了一个三准粒子激发带,并指定了它的最可能组态为π9/2~-[514](?)νAE。

Observation of Three-Quasiparticle Doublet Bands in I-123: Possible Evidence of Chirality

A new band in the odd proton nucleus I-123 is identified via in- beam gamma- ray spectroscopy using the N-14+Cd-116 reaction. This band shows up as doublets with the previously assigned pi g(7/2) circle times (nu h(11/2))(2) band. Possible configurations of the new band are discussed in the framework of the cranked shell model and the geometrical model. It is argued that the new band might be a chiral partner of the previously known pi g(7/2) circle times (nu h(11/2))(2) band.

Multi-quasiparticle gamma-band structure in neutron-deficient Ce and Nd isotopes

The newly developed multi-quasiparticle triaxial projected shell model approach is employed to study the high-spin band structures in neutron-deficient even-even Ce- and Nd-isotopes. It is observed that gamma-bands are built on each intrinsic configuration of the triaxial mean-field deformation. Due to the fact that a triaxial configuration is a superposition of several K-states, the projection from these states results in several low-lying bands originating from the same intrinsic configuration. This generalizes the well-known concept of the surface gamma-oscillation in deformed nuclei based on the ground-state to gamma-bands built on multi-quasiparticle configurations. This new feature provides an alternative explanation on the observation of two I = 10 aligning states in Ce-134 and both exhibiting a neutron character. (C) 2009 Elsevier B.V. All rights reserved.