Law of corresponding states and thermal-diffusion factor of Ne---Kr and Ar---Kr mixtures

New data of the thermal diffusion factor, α_T, for five Ne---Kr and four Ar---Kr mixtures in the low temperature range are given. It is shown that the dependence of α_T on the composition of these mixtures together with the thermodynamic and first-order transport properties of the noble gases can be interpreted consistently using the law of corresponding states proposed by Kestin, Ro and Wakeham. Moreover it is suggested that the thermal diffusion factor of these mixtures could also be interpreted by this law.     

A study of the two-bulb method for measuring diffusion coefficients of binary gas mixtures

The concentration dependences of the binary diffusion coefficients of the systems He-Ar and He-O₂ are reported at 300 K and 1 atm pressure. Two independent sets of data, obtained with a two-bulb cell and a shearing-cell of Loschmidt design, agree within the error of measurement. The data for the two-bulb cell were obtained at pressures where Knudsen effects are important. It was found necessary to improve the extrapolation procedure of van Heijningen et al. by using the results of the dusty-gas model as described by Mason et al.     

g factor measurements of high spin isomeric states in 187,189,191 Au

The g factors of three high spin isomers in ^187,189,191Au have been measured, using the time differential perturbed angular distributions. The reactions used and the results obtained for the g factors and the lifetimes are: ¹⁷²Yb(¹⁹F, 4nγ) ¹⁸⁷Au, g (31/2- or 35/2-) = 0.25 (3), T_1/2 = 102 (5) ns; ¹⁸¹Ta ( ¹²C, 4nγ) ¹⁸⁹Au, g (31/2+) = 0.42 (2), T_1/2 = 242 (10) ns; and ¹⁷⁶Yb(¹⁹F, 4nγ) ¹⁹¹Au, g (31/2+) = 0.42 (3) T^1/2 = 402 (20) ns. These results show that the structure of these isomers is consistent with a 1 proton, 2 neutrons structure. The experimental set-up was cheked by measuring the g factor of the Coulomb excited 197 keV, T_1/2 = 89.3 ns level of the ¹⁹F beam stopped in the lead backing.     

Space resolved density measurements of argon and helium metastable atoms in radio-frequency generated He-Ar micro-plasmas

Space resolved concentrations of helium He* (³S₁) and argon Ar* (³P₂) metastable atoms in an atmospheric pressure radio frequency micro-plasma jet were measured using tunable diode laser absorption spectroscopy. Even small absorptions down to 10^-4 could be measured using lock-in technique. The absolute density of metastable atoms densities at different rf-power, flow rate and gas mixture was deduced from measured absorption rates. Metastable concentrations range from 10⁹ to 10¹¹ cm^-3. Analysis of spectral profiles provided the pressure broadening coefficients of both metastable atoms by helium. The spatial distribution of metastable atoms in the plasma volume was obtained for various discharge conditions. Density profiles between the electrodes reveal the sheath structure and reflect the plasma excitation distributions in the discharge volume. It reveals the dominance of the α-mode discharge.     

The law of corresponding states for metals

Using the similarity of the effective potentials seen by ions in metals a reduced phonon equation of state is derived. It is shown that the melting point T_m(0) and the atomic volume Ω₀ at T = 0 K and at p = 0 are suitable macroscopic parameters for scaling ? and σ characterizing the interatomic potentials of metals having similar structures. The temperature and pressure dependence of thermodynamical quantities reduced with the above parameters are discussed and the results are compared with the experiment. It is shown that the pressure dependence of the reduced thermodynamic quantities can be described by the pressure dependence of the scaling parameters T_m(p) and Ω₀(p).The general form of the reduced equation of state (containing the electronic contributions as well) obtained gives that the reduced pressure is a universal function of the following reduced variables: the volume, temperature, de Broglie wavelength, Gibbs free energy of electrons $\text{3}\text{5}\text{zE}{}_{\mathrm{fo}}\text{?}$ (E_fo is the Fermi energy at T = 0 K) and depe of the valence z as well. It is shown that $\text{E}{}_{\mathrm{fo}}\text{?}$ is a function of $\text{Ω}{}_{\mathrm{o}}{}^{\mathrm{<mtext>?1</mtext><mtext>2</mtext>}}$ and $\text{(}\text{E}{}_{\mathrm{fo}}\text{/?}\text{)Ω}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ is approximately constant within the same sub-group of the periodic table.     

Properties of mixtures on non-orthogonal states

We study the density operators expressed as mixtures of non-orthogonal pure states in quantum mechanics. The general mathematical law of formation of such mixtures is found. Applications are given concerning the entropy properties of density operators etc.     

Principle of corresponding states for hard polyhedron fluids

ABSTRACT

We introduce an equation of state for hard polyhedra and validate our new theory with simulations performed for 22 different shapes spanning a range of particle anisotropy. The derived expression not only shows excellent agreement with simulations but also exhibits ‘corresponding states’-like behaviour across shape space, allowing for a systematic reduction of thermodynamic properties onto a single master curve. Additionally, we propose a scaling-type argument for predicting the order–disorder transition packing fraction for hard polyhedron fluids that accurately captures the observed transitions in simulations. Our works suggest that hard-polyhedron systems can be thought of as perturbations about a hard-sphere where corrections in the principle axes of inertia and excess volume account for differences in relative orientation between neighbouring particles and each polyhedron's intrinsic asphericity, respectively. Additionally, our theory greatly benefits from requiring only knowledge of the inherent geometry for a polyhedron of interest with no necessary fitting parameters and thus provides a good heuristic rule of thumb for targeting relevant regions of simulation interest for novel systems of hard polyhedra.     

The thermal diffusion factor of Ar-CO2 mixtures: New measurements and comparison with quantum calculations

New measurements for the thermal diffusion factor and for the diffusion coefficient derived from it are reported for the Ar-CO2 gaseous mixture at different temperatures and for various concentrations of the CO2 molecule. Several of the interaction potentials between the partners which have been suggested in the literature are examined, and quantum dynamics calculations are carried out to compare their performances using the infinite order sudden dynamic decoupling scheme. The present results are compared with other experiments and show clearly that, although one of the empirical potentials turns out to be the most realistic for describing such properties, a unique form of a multiproperty-tested potential energy surface for this system is still lacking.     

Superconductive density of states in Ag-Pb-Ag sandwiches from calorimetric measurements

The electronic excitations in Ag-Pb-Ag sandwiches were studied by means of calorimetric measurements in the temperature range 0.3–2 K. The observed specific heat reflected the existence of a gap in the excitation spectrum. A value of the BCS. interaction parameter in silver was deduced within the framework of existing theoretical models. It gave good agreement with previous determinations which proceeded from different experimental approaches.     

The extended law of corresponding states and the interaction potential

An inversion procedure is used to obtain from the extended law of corresponding states the interaction potential over a range of reduced temperature extending from 0.5 to 25. This directly determined potential is in excellent agreement with the Lee potentials in the intermediate region. The consistency between diffusion coefficients and second virial coefficients is checked.     

Some surprises of quantum measurements and states

The problem of physical reality and measurability of observables is discussed on the example of phenomena revealed by the author. The essence of the phenomena is as follows. After measurement of the coordinate, the variance of the momentum can be smaller than the initial one and depends on the result of the coordinate measurement even if the coordinate and the momentum are uncorrelated. This refers to any pair of conjugate observables, in particular, to the number of quanta and the phase. In a state with a minimum product of uncertainties of the coordinate and the momentum, the mean value of the observable ${{\left\{ {\hat x^2 ,\hat p^2 } \right\}} \mathord{\left/ {\vphantom {{\left\{ {\hat x^2 ,\hat p^2 } \right\}} 2}} \right. \kern-0em} 2}The problem of physical reality and measurability of observables is discussed on the example of phenomena revealed by the author. The essence of the phenomena is as follows. After measurement of the coordinate, the variance of the momentum can be smaller than the initial one and depends on the result of the coordinate measurement even if the coordinate and the momentum are uncorrelated. This refers to any pair of conjugate observables, in particular, to the number of quanta and the phase. In a state with a minimum product of uncertainties of the coordinate and the momentum, the mean value of the observable , which corresponds to the classical product of the squares of the coordinate and the momentum, is negative. __________ Translated from Optika i Spektroskopiya, Vol. 96, No. 5, 2004, pp. 747–750. Original Russian Text Copyright ? 2004 by Vorontsov.     

Density of states of GaAs-AlGaAs-heterostructures deduced from temperature dependent magnetocapacitance measurements

We have analyzed the density of states of a two dimensional electron gas in a GaAs-AlGaAs hetereostructure by measuring the magnetocapacitance in magnetic fields up to 6 Tesla at temperatures below 10 K. The experimental data are well described by a Gaussian-like density of states where the linewidth Γ is proportional to ✓B.     

Restoration of quantum states after measurements

 We discuss possibilities of protecting quantum states against disturbances introduced by quantum measurements. We specify conditions under which it is possible to restore an unknown state of a combined quantum system after measurements which were performed on some (but not on all) of its components. Received: 3 April 1996/Revised version: 5 July 1996     

High-pressure melting curves of argon, krypton, and xenon: deviation from corresponding states theory.

The melting curves of argon, krypton, and xenon were measured in a laser heated diamond-anvil cell to pressures of nearly 80 GPa reaching melting temperatures around 3300 K. For the three gases, we observed a considerable decrease in the melting slopes (dT/dP) from the predictions based on corresponding states scaling starting near 40, 30, and 20 GPa, respectively. The melting anomaly can be understood in terms of a model in which hcp stacking faults act as solutes in a binary system.     

The principle of corresponding states and the dynamic properties of simple liquids

We present a corresponding states analysis of existing data on sound velocity, transport coefficients and intermolecular interaction times of a number of simple fluids. With appropriate choices of parameters for the intermolecular pair potential, such properties as the adiabatic sound velocity, the shear and bulk viscosities, the thermal conductivity and the intermolecular interaction time can be reduced along the liquid-vapor equilibrium curve. Deviations from the simple law of corresponding states are most pronounced for the transport properties, indicating a stronger sensitivity of the dynamical properties to the interaction potential and the molecular structure.     

A law of corresponding states for materials at shock pressures

By introducing an adequate set of reduced coordinates, it is shown that the analytical expression for the shock Hugoniot can be put into a form containing only pure numbers and dimensionless variables. The resulting equation is valid for those materials following a linear relationship between shock and particle velocities. A law of corresponding states for materials at shock pressures is established, and it is shown that some of the similarities already reported in the literature can be obtained as particular cases of this law. The reduction parameters are interpreted in terms of a limiting value to shock compression, and of a property that might be called shock hardness of the material. It is proved that the variables introduced in this paper not only allow the representation of all the shock wave data in one single curve, but simplify considerably all the equations involved in shock problems. To illustrate the use of these equations in the treatment of the thermodynamics of high pressure, the calculation of entropy changes is finally discussed.