The non-linear dielectric effect in liquid xenon

The non-linear dielectric effect (NLDE), that is the increase in the dielectric constant divided by the square of the applied field, is measured for a number of non-polar molecular liquids and for liquid xenon. The values of the NLDE are compared with results in the literature and with values predicted by theory. The agreement with other experiments is quite good, but with theory is very poor, the only exception being Liquid xenon, where agreement is good. A possible explanation is given. The prediction that the NLDE should increase strongly near the critical point due to the divergence of the isothermal compressibility could not be established by experiment. The conclusion is drawn that this failure is due to the reduction by the theory of second-order effects to first-order thermodynamic and molecular properties.     

Non-linear density dependence of rotational line-broadening of HCl in dense argon

The rotational far-infrared spectra of HCl in argon at densities between 100 and 480 amagat and T = 162.5 K are presented. The observed density dependence of the width of the different rotational lines is non-linear and differs for high- and low-frequency lines. An Enskog correction to the collision frequency in the dense gas fails to account for the density dependence of the high rotational lines. It is argued that the many-body character of the relaxation mechanism should be taken into account. Comparison with the results of MD calculations on argon indicates that such an approach may explain the observed density dependence.     

Molecular dynamics calculations on the time dependence of simple,anisotropic potentials in dense argon

Molecular dynamics calculations on the time dependence of the anisotropic potential experienced by a probe molecule in argon, are presented. The calculations were performed for Ar densities of 100, 300, 500 and 784 amagat and T = 160 K. Collective motions clearly manifest themselves at higher densities, in particular in the power-spectrum of the part of the anisotropic potential that transforms as an irreducible tensor of rank 1. The relation between time-dependent local anisotropy and a number of experiments is discussed.     

The far-infrared spectrum of hydrogen chloride in liquid xenon

The absorption spectrum of hydrogen chloride in liquid xenon in the region between 10 and 240 cm^?1 is reported. The spectrum shows a residual rotational fine structure that is even more pronounced than the fine structure in the corresponding spectra in lighter noble gas liquids. Therefore there is no positive correlation with the atomic polarizabilities.     

Approximate Monotonicity: Theory and Applications

The ideas of value distribution for measurable functions fromR to R are applied to functions which are approximately monotonicon sets of positive measure. (For definitions see 1.) A functionp(x) is introduced, describing the local relative value distributionin the neighbourhood of a point x, and it is shown that almosteverywhere p(x) = 0 or wherever p(x) exists, implying approximate differentiability, with thefunction approximately oscillatory elsewhere. These resultsare applied to the analysis of angular boundary behaviour forHerglotz functions, where they have implications for the spectralanalysis of differential and other operators.     

Phonon-phonon scattering cross-sections from crossed phonon beams

In two crossed phonon beams generated by heatpulses the attenuation of high frequency phonons by phonon-phonon interaction was observed for the slow transverse phonons of the [1 1 0] branch of Si at 3.6 K. From the experimental data the phonon scattering cross-section for a three phonon normal process can be calculated.     

Temperature dependence of the pressure induced width and shift of the first HCl rotational line

The line widths and frequencies of the j = 0 → j = 1 pure rotational line of HCl in a gaseous mixture with argon at different pressures and different temperatures are reported and compared with existing theories.     

Eight-point density correlation functions in lennard-jones fluids

Molecular dynamics calculations of components of the eight-point four-time density correlation function around a probe mulecule in a Lennard-Jones host fluid have been made. This function has important consequences for the interpretation of line broadening and other collision-induced spectroscopic experiments.     

The freezing of supercooled water

The onset of crystallization of supercooled water upon lowering the temperature is highly unpredictable, depending strongly on the specific sample and its treatment. The mechanism causing this is to be investigated and may be found in terms of the dependence of the transition temperature on the shear acting in the convecting liquid. This effect of shear on the fluctuation spectrum is considered qualitatively.