Brillouin scattering in liquid sulfur dioxide: relaxational behaviour

The frequency dependence of hypersonic absorption and the dispersion of hypersonic speed in liquid sulfur dioxide (SO₂) were determined at (293.75±0.30) K and at (284.65±0.30) K by Brillouin spectroscopy. The results are used to experimentally establish the second relaxation step in the double vibrational relaxation of these quantities in the liquid phase, which was first conjectured by R. Bass and J. Lamb, Proc. R. Soc. Ser. A (1958) 243, 94. This second relaxation takes place at approximately 1.5 GHz for both temperatures within experimental error, whereas the first relaxation step, previously determined by ultrasonic spectroscopy, takes place at approximately 23 MHz. In the course of this investigation, some evidence was found that for the temperatures considered the shear viscosity relaxes in the hypersonic frequency range.     

Antiferromagnetic ordering in magnetic ionic liquid Emim[FeCl4]

The magnetic ionic liquids (MILs) are considered to open up a wide range of applications because of their magnetic and electrochromic switching. Until recently almost all magnetic ionic liquids containing tetrachloroferrate ion FeCl₄⁻ evidenced a paramagnetic temperature dependence of the magnetic susceptibility, with only small deviations from the Curie law at low temperatures. However, 1-ethyl-3-methylimidazolium tetrachloroferrate, Emim[FeCl₄], clearly exhibits a long-range antiferromagnetic ordering below the Neel temperature T_N≈3.8 K. In addition, the shape of the magnetic ordering depends on the cooling speed, indicating that the magnetic coupling could be modified.     

Non-hydrodynamic modes in viscoelastic behaviour of simple fluids

ABSTRACT

We discuss the role of non-hydrodynamic processes in viscoelastic transition in pure liquids. In particular, using both analytical results and molecular dynamics simulations, we clarify the effect of the shear stress relaxation on the transverse dynamics. We use as an example the Lennard-Jones fluids. We analyse the frequency dependence of the shear modulus and its connection to the non-hydrodynamic shear relaxation mode. The analysis of the relaxation times of the non-hydrodynamic modes in longitudinal and transverse dynamics makes evidence that the emergence of the non-hydrodynamic transverse excitations outside the propagation gap is not directly connected to the onset of the positive sound dispersion.     

Study of clusters of interest for liquid ionic alloys

Calculations are reported of the total energies and related quantities of sequences of small clusters of the form A_m Pb_n, where A is an alkali atom, n <6 and m < 9. The object of this study is to shed light on the stoichiometry and the possible formation of complexes in A-Pb liquid alloys. The calculations are performed using empty core pseudopotentials and the spherical average approximation for the cluster. The results are insensitive to the choice of alkali atom apart from a smooth trend with the progression from Li to Cs. The calculated total energies suggest that clusters with compositions A₄Pb and A₄Pb₄ are very stable against a change in the number of Pb or A atoms and support the possibility of these clusters forming in the liquid alloys. This stability arises from an electronic shell-closing effect.     

Coulometry on the Voltammetric Timescale: Microdisk Potential‐Step Chronoamperometry in Aprotic Solvents Reliably Measures the Number of Electrons Transferred in an Electrode Process Simultaneously with the Diffusion Coefficients of the Electroactive Species

Microdisk, single potential‐step chronoamperometry, is applied to a range of organic substrates in the aprotic solvents tetrahydrofuran, propylene carbonate, acetonitrile and the room temperature ionic liquid [C₄dmim][N(Tf)₂]. Fitting of the chronoamperometric transients was achieved using the Shoup and Szabo method [3]. Accurate values for the diffusion coefficients, D, and the number of electron(s) transferred, n, in the electrode process have been simultaneously and consistently obtained. This method is shown to be generally applicable and reliable for the determination of the number of electrons transferred in faradaic processes uncomplicated by relatively slow coupled homogeneous kinetics. Since the experiment is conducted essentially on typical voltammetric timescales it can be commended as a complementary technique for classical coulometry which is only possible on much longer timescales. The chronoamperometric method is therefore likely to be of greater relevance to the interpretation of voltammetric data.     

Preparation of nano-sized functional materials using laser ablation in liquids

We propose a convenient technique applicable for investigations of various functions of nanoparticles produced by laser ablation in liquids. It was demonstrated that nanoparticles of anatase-TiO₂, a electrode material for lithium secondary batteries, produced by laser ablation in acetone could be efficiently deposited on a substrate by using an electrophoresis technique. Analysis of the electrochemical properties of nanoparticles become much more facile with those deposited nanoparticles than with dispersed nanoparticles. In addition, it was demonstrated that comparison of the electrochemical properties between nanoparticles and microparticles were possible by means of this technique.     

手性离子液体在有机合成中的应用

近年来,手性离子液体的应用研究取得了重要进展,新的手性离子液体的不断涌现促使人们对其应用研究的兴趣不断提高.本文综述了手性离子液体在有机合成中应用研究的新进展.     

Proposed lower bound for the shear viscosity to entropy density ratio in some dense liquids

Starting from relativistic quantum field theories, Kovtun et al. (2005) have quite recently proposed a lower bound η/s??/(4πkB), where η is the shear viscosity and s the volume density of entropy for dense liquids. If their proposal can eventually be proved, then this would provide key theoretical underpinning to earlier semiempirical proposals on the relation between a transport coefficient η and a thermodynamic quantity s. Here, we examine largely experimental data on some dense liquids, the insulators nitrogen, water, and ammonia, plus the alkali metals, where the shear viscosity η(T) for the four heaviest alkalis is known to scale onto an ‘almost universal’ curve, following the work of Tankeshwar and March a decade ago. So far, all known results for both insulating and metallic dense liquids correctly exceed the lower bound prediction of Kovtun et al.     

Chemical physics of liquids (A statistical mechanical version of liquids)

The liquids differ from gases and solids in that they are neither completely ordered like the latter nor completely disordered like the former. Thus they have only short range order and long range disorder. Nevertheless much progress has been made in understanding liquids during the last one and half decades. This paper reviews the progress made in this field including the contributions made by the author and his group.