Quantum tunneling of the magnetic moment in a free nanoparticle

We study tunneling of the magnetic moment in a particle that has full rotational freedom. Exact energy levels are obtained and the ground-state magnetic moment is computed for a symmetric rotor. The effect of mechanical freedom on spin tunneling manifests itself in a strong dependence of the magnetic moment on the moments of inertia of the rotor. The energy of the particle exhibits quantum phase transitions between states with different values of the magnetic moment. Particles of various shapes are investigated and the quantum phase diagram is obtained.     

Infrared laser spectroscopy of diacetylene and cyclopropane in helium nanodroplets

High resolution infrared laser spectroscopy has been used to obtain rotationally resolved vibrational spectra of diactyelene and cyclopropane in helium nanodroplets. In part, this work was motivated by the need for a large database of rotational constants for molecules solvated in liquid helium. Data of this type provides benchmarks with which to test the theoretical methods that are currently being developed for calculating the effect of the helium on the rotational dynamics of these solvated molecules. In general, the correlated motion of the helium and the molecule results in an effective moment of inertia that is considerably larger than that of the gas phase molecule.     

Fully quantum mechanical moment of inertia of a mesoscopic ideal Bose gas

The superfluid fraction of an atomic cloud is defined using the cloud's response to a rotation of the external potential, i.e. the moment of inertia. A fully quantum mechanical calculation of this moment is based on the dispersion of L_z instead of quasi-classical averages. In this paper we derive analytical results for the moment of inertia of a small number of non-interacting Bosons using the canonical ensemble. The required symmetrized averages are obtained via a representation of the partition function by permutation cycles. Our results are useful to discriminate purely quantum statistical effects from interaction effects in studies of superfluidity and phase transitions in finite samples. Received 30 June 2000     

中子星的转动惯量与表面红移的研究

在温度、密度及同位旋相关的核物质状态方程的基础上,通过求解Tolman–Oppenheimer–Volkoff方程,得到了中子星的转动惯量与表面红移.计算结果表明,中子星的转动惯量较强地依赖于核物质的不可压缩系数与对称能强度系数,而对核子有效质量不太敏感;中子星的表面红移却对对称能强度系数不太敏感,而较强地依赖于不可压缩系数与核子有效质量.     

转动惯量平行轴定理验证实验的改进方案

本文介绍了一种刚体转动惯量平行轴定理验证实验的改进方案.该方案通过调节对称放置在承物台上的两个钢柱到仪器转轴的距离来改变系统的转动惯量,使得总转动惯量可以在较大的范围内改变,并且始终保持了系统质量的对称性分布,从而有效地减小了实验的相对误差,提高了实验结果的可信度.     

The evolution of the molecular relaxation parameters described by the Cole–Cole model at the isotropic-nematic phase transition*

This paper presents the dielectric properties of the isotropic liquid and nematic phase at the phase transition. One strong molecular relaxation is observed in both phases. It is interpreted as related to the relaxation around a short molecular axis, due to the fact that molecules possess a strong longitudinal dipole moment. In the isotropic liquid the relaxation is described by the Debye model, while after entering the nematic phase (at cooling) relaxation becomes described by the Cole–Cole model. The distribution parameter of the Cole–Cole model changes from 0.05 (10 degrees above the temperature of the Iso-N transition) to 0.09 (exactly at the phase transition Iso-N), and finally, it reaches 0.35 (10 degrees below the Iso-N transition). Additionally, we observe that ion contribution to the dielectric response is not influenced by the phase transition. All relaxation parameters are discussed within the context of the phase transition phenomena.     

On the moment of inertia of a proto neutron star

The influences of σ* and Φ mesons,temperature and coupling constants of nucleons on the moment of inertia of the proto neutron star(PNS) are examined in the framework of relativistic mean field theory for the baryon octet {n,p,Λ,Σ+,Σ0,Σ+,Ξ-,Ξ0} system.It is found that,compared with that without considering σ* and Φ mesons,the moment of inertia decreases.It is also found that the higher the temperature,the larger the incompressibility and symmetry energy coeficient,and the larger the moment of inertia of a PNS.The influence of temperature and coupling constants of the nucleons on the moment of inertia of a PNS is larger than that of the σ* and Φ mesons.     

Molecular dynamics study of electron gas models for liquid water

The frozen density electron gas model proposed by Gordon and Kim for rare gas systems has been implemented in a molecular dynamics code. This code has been applied to investigate various options for extending this scheme to inter-molecular interactions in liquid water. We have compared a number of gradient corrections to the Thomas-Fermi kinetic energy. We also explored a more empirical approach based on adaptation of the frozen molecular electron density to the condensed phase environment. Consistent with experience from force field methods, enhancement of the molecular dipole moment proved to be necessary to reproduce the properties of the liquid. The best models we investigated are a gradient corrected expansion of the simple local density Hamiltonian applied in the original Gordon and Kim model. In addition, these models observed a modified molecular electron density carrying the same dipole moment of 2.95 D as has been observed by recent ab initio molecular dynamics studies based on fully self-consistent Kohn-Sham methods. Possible implications of this finding for force field models are discussed.     

On the moment of inertia of a quantum harmonic oscillator

An original method for calculating the moment of inertia of the collective rotation of a nucleus on the basis of the cranking model with the harmonic-oscillator Hamiltonian at arbitrary frequencies of rotation and finite temperature is proposed. In the adiabatic limit, an oscillating chemical-potential dependence of the moment of inertia is obtained by means of analytic calculations. The oscillations of the moment of inertia become more pronounced as deformations approach the spherical limit and decrease exponentially with increasing temperature.     

扭摆系统中扭杆的等效转动惯量——圆柱杆扭转振动的研究

研究扭摆系统中扭杆的质量或转动惯量对扭摆运动的影响,引入一个概念:扭摆系统中扭杆的等效转动惯量.纠正了一些文献在相关问题上的误解.     

Influence of the moment of inertia of the pendulum on the internal friction (loss tangent) measured by free decay

Summary The internal friction (loss tangent) of solids is normally measured, as a function of temperature, with a torsion pendulum operating in free decay. Curves of the internal friction and the oscillation frequency, against temperature, are obtained at various moments of inertia, to extract the parameters characteristic of the relaxation process (relaxation time and strength). In all these experiments only the temperature is considered as an independent variable and the moment of inertia of the pendulum is mainly used to shift the internal friction peaks in the temperature scale. It is pointed out in the paper that the moment of inertia is also an independent variable which can be used to determine, with high accuracy, if the measured peak is of the Debye type or not. A new torsion pendulum, with continuously variable moment of inertia is presented, which allows measurements of the partial derivative of the internal friction and the oscillation frequency with respect to the moment of inertia, at constant temperature. Finally, some measurements of the Snoek relaxation in Nb-O alloys are presented, to show the applicability of the concepts developed in the paper. The authors of this paper have agreed to not receive the proofs for correction.     

切变模量和转动惯量实验的改进

设计了一种基于垂直轴定理的新型吊钩,对切变模量和转动惯量实验进行了改进,使之成为既可测定金属丝切变模量和环、柱等刚体的转动惯量,又可验证反映转动惯量重要性质的平行轴定理及垂直轴定理的多功能实验仪.     

刚体绕任意轴转动惯量的简便计算

利用微元求和的方法给出几种刚体对于过质心任意轴的转动惯量公式，并由此引出转动惯量与刚体几何对称性的联系，以及与转动惯量有关的几何形体等价性的一些结果．     

Continuum model for polymorphism of bacterial flagella

Bacterial flagellar filaments can abruptly change shape in response to mechanical load or changes in solution pH or ionic strength. These polymorphic transformations are an instance of a ubiquitous phenomenon, the spread of conformational change in large macromolecular assemblies. We propose a new theory for polymorphism, whose essential elements are two molecular switches and an elastic mismatch strain between the inner and outer cores of the filament. We calculate the phase diagram for helical and straight states, and the response of a helical filament to an external moment.     

Properties of rotational excitations in odd mass Dy isotopes

The data on high-spin rotational states in¹⁵⁵Dy,¹⁵⁷Dy,¹⁵⁹Dy and¹⁶¹Dy are discussed within a model where a particle is coupled to a rotor with a variable moment of inertia. In this model there is often a definite improvement in the quality and stability of the fits to levels in the positive-parity band below spin 25/2 when the moment of inertia of the core exhibits a linear dependence on the square of the rotational angular velocity as compared to the situation where a linear dependence onI(I+1) is assumed. In the improved fits the empirical matrix elements of the Coriolis force exhibit a smooth and significant increase with decreasing moment of inertia. The rotational energies above spin 25/2 in the positive-parity band and above 19/2 in the 11/2^? [505] band are understood within the present theoretical model if the moment of inertia increases more rapidly than the linear trend established at lower spin. In the 11/2^? [505] band this increase follows rather closely the behaviour in the even nuclei whereas in the positive-parity band the curves are quite flat even beyond the point where the moment of inertia in the even nuclei exhibits a discontinuous or back-bending behaviour. The significance of this observation is discussed in the light of existing theories on nuclear moments of inertia.     

Slow rotation in the bimetric theory of gravitation

The equations describing the moment of inertia and the dragging of inertial frames of slowly rotating neutron stars are derived according to Rosen's bimetric theory of gravitation. Numerical calculations of the properties of neutron stars according to the bimetric theory and general relativity were made using several equations of state. The general trend found is that in the bimetric theory neutron stars with a given mass induce a smaller dragging of inertial frames than in general relativity. The moment of inertia of low-mass stars also is smaller in the bimetric theory. For high-mass stars, however, the moment of inertia is found to be larger in the bimetric theory.In partial fulfillment of the requirements for the D.Sc. degree.     

Zeeman effect in the N.Q.R. of 81Br in single crystals of 2,4-dibromoanisole and 2,4,6-tribromoanisole

The influence of the intramolecular degrees of freedom on the vapour–liquid equilibrium properties of ammonia is studied for vapour pressure, saturated densities and enthalpy of vaporization. Molecular force fields with and without intramolecular degrees of freedom, keeping all other parameters unchanged, show significantly different phase envelopes. For ammonia, the angle potential is particularly important, because the hydrogen sites are more aligned in the liquid than in the vapour, leading to a significantly enhanced molecular dipole moment in the condensed phase. Based on a rigid force field for ammonia from prior work of our group [Eckl et al., Mol. Phys. 106, 1039 (2008)], a new accurate force field with intramolecular degrees of freedom is developed.     

Description of the Superdeformed Bands in A～190 Region with a Three-Parameter Formula

The q-deformed moment of inertia, formulated by was first introduced as the mechanical moment of inertia of superdeformed (SD) nuclei. The E2 transition γ-ray energies and the dynamical moment of inertia of the lowest-formed bands in Hg, Ph, and TI isotopes are calculated. The calculated results indicate that the SD bands may be described by the ided-rotor with the q-deformed mpment of inertia.     

分形物体转动惯量的计算

由分形物体的自相似性、转动惯量的量纲和平行轴定理,分别计算并得到分形三角形、分形正方体、分形四面体和科赫雪花的转动惯量.     

基于电力线载波与TCP/IP协议的刚体转动惯量实验系统的设计

介绍了一种新的测量刚体转动惯量的实验方法与实验装置,在实验中,通过增加标准刚体试件,把细线拉力对转轴摩擦力矩的影响考虑进去,大幅度地提高了实验测试精度,另外,利用电力线载波通讯网络,将转动惯量测量仪采集的时间数据传输到PC机中,再经过PC机端数据处理软件,快速准确地将待测刚体的转动惯量以及其它与刚体有关的物理量计算、显...