Temporal coherence of sound transmissions in deep water revisited

This paper examines the signal coherence loss due to internal waves in deep water in terms of the signal coherence time and compare to data reported in the literature over the past 35 years. The coherence time of the early raylike arrivals was previously modeled by Munk and Zachariasen ["Sound propagation through a fluctuating stratified ocean: Theory and observation," J. Acoust. Soc. Am. 59, 818-838 (1976)] using the supereikonal approximation and by Dashen et al. ["Path-integral treatment of acoustic mutual coherence functions for arrays in a sound channel," J. Acoust. Soc. Am. 77, 1716-1722 (1985)] using the path integral approach; a -1 [corrected] power frequency dependence and a -1/2 [corrected] power range dependence were predicted. Recent data in shallow water in downward refractive environments with internal waves suggested that the signal coherence time of the mode arrivals follows a -3/2 power frequency dependence and a -1/2 power range dependence. Since the temporal coherence of the acoustic signal is related to the temporal coherence of the internal waves, based on the observation that the (linear) internal waves in deep and shallow waters have a similar frequency spectrum, it is argued that the modelike arrivals in deep water should exhibit a similar frequency dependence in deep and shallow waters. This argument is supported by a brute-force application of the path integral to mode arrivals based on the WKB relation between the ray and mode. It is found that the data are consistent with the -3/2 power frequency dependence but more data are needed to further test the hypothesis.     

Incident angle dependence of electronic desorption and sputtering by energetic ions

It is shown that deviations of the dependence of sputtering yield on the incident angle, θ, from the standard (cos θ)⁻¹ dependence can be indicative of a depth dependence in the net energy deposition in the surface region. Information about the sputter ejection mechanism is shown to be obtained only secondarily. We give expressions that allow one to relate the measured dependence of the yields on angle of incidence to the dependence of energy deposition on depth. This is used to analyze results for condensed gas sputtering and heavy ion desorption of organic molecular ions. This analysis indicates that the spatial distribution of excitations produced by the secondary electrons is important in determining these yields. This is also confirmed by observed differences in the yields for transmission and back-sputtering which is a closely related effect.     

An analysis of nuclear charge radii based on the empirical formula

Several nuclear charge radii had been calculated based on the law of A1/3 and isospin dependence Z1/3 formula which had been used to describe the charge radii data. It is achieved that the isospin dependence Z1/3 formula is superior to the generally accepted A1/3 law through mean root square deviation analysis, that is, the Z1/3 formula is more effective to describe the charge radii data.     

Electrical control of spin relaxation in a quantum dot

We demonstrate electrical control of the spin relaxation time T1 between Zeeman-split spin states of a single electron in a lateral quantum dot. We find that relaxation is mediated by the spin-orbit interaction, and by manipulating the orbital states of the dot using gate voltages we vary the relaxation rate W identical withT1(-1) by over an order of magnitude. The dependence of W on orbital confinement agrees with theoretical predictions, and from these data we extract the spin-orbit length. We also measure the dependence of W on the magnetic field and demonstrate that spin-orbit mediated coupling to phonons is the dominant relaxation mechanism down to 1 T, where T1 exceeds 1 s.     

An analysis of nuclear charge radii based on the empirical formula

Several nuclear charge radii had been calculated based on the law of A^1/3 and isospin dependence Z^1/3 formula which had been used to describe the charge radii data. It is achieved that the isospin dependence Z^1/3 formula is superior to the generally accepted A^1/3 law through mean root square deviation analysis, that is, the Z^1/3 formula is more effective to describe the charge radii data.     

Polarization dependence of optical transitions in GaP(1 1 0) and GaAs(1 1 0) surfaces studied with surface differential reflectivity

We present results on the polarization dependence of Surface Differential Reflectivity in GaP(1 1 0) and GaAs(GaAs(1 1 0) surfaces. GaP(1 1 0) shows a transition at 2.8 eV which is excited only with the light electric vector parallel to the [1 1 0] direction; for the optical transition above 3.0 eV there is not any marked polarization dependence. GaAs(1 1 0) shows optical transitions between 2.6 and 4.0 eV which have a weak dependence on light polarization.     

Effect of thermal nonlinearity in high-absorption media on the parameters of the photoacoustic signal detected by the gas microphone method: The fundamental and second harmonics

A perturbation theory is put forward that describes the effect of thermal nonlinearity due to the temperature dependence of the thermophysical parameters of high-absorption systems with a low thermal conductivity on the parameters of the photoacoustic signal detected by the gas microphone technique. It is found that the dependence of the photoacoustic signal amplitude on incident beam intensity I ₀ stems from the dependence of the illuminated surface temperature on I ₀. This dependence is a complicated function instead of being a simple quadratic function as was expected. In the limiting cases (μ_sβ ? 1 and μ_sβ ? 1), this contribution to the photoacoustic signal amplitude is described by simple expressions, which are convenient for determining the thermal coefficients of the thermophysical parameters of the medium. It is found that the thermal nonlinearity significantly affects the photoacoustic signal phase in the frequency region meeting the condition μ_sβ ～ 1. In the above limiting cases, its effect is insignificant. A theory of generation of the photoacoustic signal second harmonic is proposed. The second harmonic is related to the temperature dependence of the thermophysical parameters of the buffer gas and sample. It is shown that the amplitude of the signal is a quadratic function of the incident beam intensity and varies with its frequency as ω^?3/2 for μ_sβ ? 1 and ω^?5/2 for μ_sβ ? 1.     

Decomposition of the equation of state of asymmetric nuclear matter into different spin-isospin channels

We investigate the equation of state of asymmetric nuclear matter and its isospin dependence in various spin-isospin ST channels within the framework of the Brueckner-Hartree-Fock approach extended to include a microscopic three-body force (TBF). It is shown that the potential energy per nucleon in the isospin-singlet T=0 channel is mainly determined by the contribution from the tensor SD coupled channel. At high densities, the TBF effect on the lsospin-triplet T=1 channel contribution turns out to be much larger than that on the T=0 channel contribution. At low densities around and below the normal nuclear matter density, the isospin dependence is found to come essentially from the isospin-singlet SD channel and the isospin-triplet T=1 component is almost independent of isospin asymmetry. As the density increases, the T=1 channel contribution becomes sensitive to the isospin asymmetry and at high enough densities its isospin dependence may even become more pronounced than that of the T=0 contribution. The present results may provide some microscopic constraints for improving effective nucleon-nucleon interactions in a nuclear medium and for constructing new functionals of effective nucleon-nucleon interaction based on microscopic many-body theories.     

On the Temperature Dependence of Radiationless Electron Transitions. I. The Morse Oscillator Model in case of a Small Value of the Parameter Z

A number of experimental results have been recently made available on the temperature dependence of lifetimes of excited states of polyatomic molecules in condenced^1–6 and gaseous phases. The dependence was shown to be quite substantial in experiments with both fluorescence^5,6 and phosphorescence^1–4 temperature quenching. The decay-rate constant of electronic excitation is 1/τ′ = β + 1/τ, where b is determined by radiative processes and is but slightly temperature-dependent^5,6. As for the rate constant 1/τ of radiationless electronic transitions, it might be the very parameter that governs the temperature dependence of 1/τ.     

The kinetics of an atom diffusing in one dimension: Hydrogen in quartz

Abstract

The time dependence of frequency recovery at 306 K of pulse-irradiated quartz is analyzed and shown to be inconsistent with the diffusion of a specie in three dimensions, but follows well diffusion in one dimension. The main feature which distinguishes these cases is a t ^?1/2 time dependence of the recovery. No extended region for a t ^?1/2 dependence is possible in three-dimensional diffusion. An extensive t ^?1/2 dependence is predicted in one-dimensional diffusion, paralleling the observation that this holds for some three decades in time and over 80% of the recovery.

Having established one-dimensional diffusion in frequency recovery, it is shown that acoustic relaxation found at 115 K and a long time component of conductivity recovery found near 300 K, as well as the frequency recovery, all appear to originate in a common mechanism—the diffusion of H⁺ in one dimension with an activation of approximately ¼ electron volt.     

Dependence on dilution of critical and compensation temperatures of a two-dimensional mixed spin-1/2 and spin-1 system

In this study, dependence on site dilution of critical and compensation temperatures of a two-dimensional mixed spin-1/2 and spin-1 system has been investigated with Monte Carlo simulation. The dependence of the thermal and magnetic behaviors on dilution of mixed spin system has been discussed. We have shown that the critical and compensation temperatures of diluted mixed spin system linearly decrease with increasing number of diluted sites.     

超巨磁电阻材料Pr2/3Sr1/3MnO3薄膜输运性质的研究

对1/f噪声缺口的超巨磁电阻Pr_2/3Sr_1/3MnO₃薄膜样品从10K到室温的热电势值进行了测量，热电势为负值，低温下随温度线性变化，表现为金属扩散热电势，在150K开始急剧减小，过渡到与温度T成反比的变化关系，与小极化子模型相符.结合在电阻极大温度附近对电阻和1/f噪声行为的讨论，对于发生在电阻极大温度附近的相变过程，结果支持源于相分离的渝渗模型. 关键词： 稀土锰氧化物 热电势 渝渗模型     

Electronic specific heat of nanographite ribbons

The electronic specific heat of nanographite ribbons exhibits rich temperature dependence, mainly owing to the special band structures. The thermal property strongly depends on the geometric structures, the edge structure and the width. There is a simple relation between the ribbon width and the electronic specific heat for the metallic or semiconducting armchair ribbons. However, it is absent for the zigzag ribbons. The metallic armchair ribbons exhibit linear temperature dependence. The semiconducting armchair ribbons exhibit composite behavior of power and exponential functions. As for the zigzag ribbons, the temperature dependence of the specific heat is proportional to T^1−p. The value of p quickly increases from to 1 as the ribbon width gradually grows. The zigzag ribbons might be the first system which exhibits the novel temperature dependence. The nanographite ribbons differ from an infinite graphite sheet, which illustrates that the finite-size effects are significant.     

On the energy dependence of the real part of the heavy-ion optical potential

The energy dependence of the real part of the heavy-ion optical potential is attributed to the J(J + 1) dependence of the-potential which is caused by the rotation induced during the collision. The magnitude and the form of the energy dependence are calculated for several light nucleus-nucleus systems with the use of the distortion potential which is defined by the diagonalization of the coupling interaction. It is shown that the heavy-ion scatterings with the inelastic channels of high and low excitation energies lead to weak and strong energy dependence of the potential, respectively.     

Log-T dependence in the low-temperature resistivity of Sb doped Si

We have studied temperature dependence of the resistivity of Sb doped Si at low temperature down to 10mK. In the vicinity of metal-nonmetal transition in Sb doped Si, the low-temperature resistivity in a just metallic side shows a logarithmic increase with lowering temperature. After thermal annealing the log-T dependence disappears and $\text{T}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ dependence is observed in the same temperature region. We find that the log-T dependence in the low-temperature resistivity comes from a surface-related conduction.     

CdS_xSe_（1－x）纳米微晶的辐射跃迁过程

利用变温吸收光谱和光致发光光谱研究了ＣｄＳｘＳｅ（１－ｘ）纳米微晶的辐射跃迁过程．由Ｖａｒｓｈｎｉ公式，拟合了微晶的吸收峰随温度的变化．根据变温发射光谱，研究了发光峰位置和温度的依赖关系，并分析了吸收峰和发光峰随温度变化的快慢．对发光的动力学过程．作了简单的分析．     

Dehydration and recrystallization of radiation-damaged titanite under thermal annealing

Abstract

Dehydration of oriented sections of a radiation-damaged titanite crystal, CaTiSiO₅, at temperatures up to 1500K was analysed using infrared spectroscopy. The IR spectra of the untreated sample show only a very weak orientational dependence. The absence of sharp absorption peaks at wave number near 3486 cm^?1 in metamict titanite shows that the local environmental configurations of OH species in the metamict titanite differ strongly from that of crystalline titanite. The OH spectra of radiation-damaged titanite can be decomposed into two components: the first component shows anisotropic and sharp spectral features while the second component consists of a broad spectral feature like those observed in disordered silica glasses. It is proposed that the first component is related to the crystalline part of the titanite sample while the second is from the defected and disordered part which suffered strong radiation damage. With increasing annealing temperature, a decrease in the broad absorption between 2500 and 3200 cm^?1 is accompanied by a recovery of sharp IR bands near 3486 cm^?1 which display the same orientational dependence as undamaged single crystals. Annealing the sample at 1000K leads to the line profiles and orientational dependence of the main OH stretching bands near 3486cm^?1 that are virtually identical with those of crystalline, undamaged titanites. At temperatures above 1500 K, the crystal starts to melt and the orientational dependence of the IR absorption is destroyed. The recrystallization processes are quantified and discussed in terms of a percolation behaviour of amorphous and crystalline titanite. It is proposed that hydrogen transport is strongly enhanced during recrystallization.     

Magnetic contribution to the Gibbs energy of elements versus temperature and pressure

A model for the pressure and temperature dependence of the magnetic contributions to the Gibbs energy of ferromagnetic and antiferromagnetic elements is presented. These contributions are described by three parameters: (1) a critical temperature which is represented by the Curie temperature for ferromagnetic elements or Néel temperature for antiferromagnetic elements, (2) the pressure dependence of that critical temperature, (3) the average magnetic moment per atom. Using thermal expansion data, all these parameters and consequently the pressure and temperature dependence of the magnetic contribution can be calculated. Nickel, a ferromagnetic element, is used as an example.     

Pressure dependence of the E1 gap in GaSb: Resonant Raman technique

A new method to determine the pressure dependence of energy gaps with the help of the diamond anvil cell is reported. The method is based on resonance Raman scattering observed as the gap energies cross the photon energies of several laser line. The technique is illustrated by means of measurements of the pressure dependence of the E₁ gap of GaSb up to the phase transition (7.7 Gpa). A sublinear dependence of the E₁ gap on pressure and a linear dependence on lattice constant (dE₁/dlnV = 4.67 ± 0.1 eV) is obtained. These results are well explained by pseudopotential calculations.     

Phonon spectrum of a naphthalene crystal at a high pressure: Influence of shortened distances on the lattice and intramolecular vibrations

The Raman spectra of a naphthalene crystal have been measured at room temperature in the pressure range up to 20 GPa. The pressure shift and Grüneisen parameters for intermolecular and intramolecular phonons have been determined. The maximum rate of the pressure shift for intermolecular phonons is 44 cm^?1/GPa, and the rate of the pressure shift for intramolecular phonons lies in the range from 1 to 11 cm^?1/GPa for different modes. The pressure dependence of the phonon frequencies for direct and inverse pressure variations has a hysteresis in the pressure range from 2.5 to 16.5 GPa. It has been shown that the linear dependence of the intermolecular phonon frequency on the crystal density has a peculiarity, which indicates a possible phase transition at a pressure of 3.5 GPa. The pressure dependence of intramolecular phonons related to the stretching vibrations of hydrogen atoms exhibits features that are characteristic of intermolecular phonons, which is associated with the influence of shortened distances between the hydrogen atoms of the neighboring molecules on the intermolecular interaction potential.