Interchange-tunneling splitting in HCl dimer in helium nanodroplets

Midinfrared spectra of HCl dimers have been obtained in helium nanodroplets. The interchange-tunneling (IT) splitting in the vibrationally excited state of the bonded H-Cl stretching band (nu(2)) in (H(35)Cl-H(37)Cl) dimers was measured to be 2.7+/-0.2 cm(-1), as compared to 3.7 cm(-1) in free dimer. From the splitting, the strength of the IT coupling in liquid helium of 0.85+/-0.15 cm(-1) was obtained, which is about a factor of 2 smaller than in the free dimer. The results are compared with the previous spectroscopic study of (HF)(2) in He droplets as well as the theoretical study of (HF)(2) and (HCl)(2) dimers in small He clusters.     

Theoretics of remote acoustic monitoring of the level and density of fluid contacting media at the interface

We present a method for monitoring the physical parameters of a medium, based on processing of an acoustic signal reflected from the studied medium. The method makes it possible to rapidly and simultaneously measure the level and density of the reflecting medium owing to acoustic sounding with pulses of different shape. We have obtained the analytic dependences relating the controlled parameters to the phase and amplitude spectra components of the reflected acoustic signal.     

Study of HCl clusters in helium nanodroplets: experiments and ab initio calculations as stepping stones from gas phase to bulk

Presented here are the results of the joint theoretical and infrared laser spectroscopic study of the hydrogen chloride monomer and clusters, (HCl)n (n=1-6), isolated in helium nanodroplets. The H-Cl stretching bands of the dimers and trimers show a large increase in the band intensity as well as low frequency shift with respect to that in a single HCl molecule. The average frequency of the bands for clusters larger than trimers remains approximately constant, which correlates well with the onset of the folded cyclic structure and the full development of the hydrogen bonding in larger clusters. The structure of the clusters was found to be cyclic planar for trimers, slightly twisted square planar for tetramers, envelope-like for pentamers, and folded pseudobipyramidal for hexamers. This change in structure upon an increase of the cluster size can be seen as an early stage of the structural transition to the HCl solid, which consists of zigzag chains of HCl molecules. Spectra of large clusters of about 500 molecules consist of a single band, which encompasses the same frequency range of trimers through hexamers.     

Thermochemical study of the reactions of acid–base interaction in an aqueous solution of α-aminobutyric acid

The heat effects of the interaction between a solution of α-aminobutyric acid and solutions of HNO₃ and KОН are measured by means of calorimetry in different ranges of рН at 298.15 K and values of ionic strength of 0.25, 0.5, and 0.75 (KNO₃). The heat effects of the stepwise dissociation of the amino acid are determined. Standard thermodynamic characteristics (Δ_r H ⁰, Δ_r G ⁰, and Δ_r S ⁰) of the reactions of acid–base interaction in aqueous solutions of α-aminobutyric acid are calculated. The connection between the thermodynamic characteristics of the dissociation of the amino acid and the structure of this compound is considered.     

Experimental study of ultrasmall-angle scattering of electron bremsstrahlung gamma-quanta (<Emphasis Type="Italic">E</Emphasis><Subscript><Emphasis Type="Italic">e</Emphasis></Subscript> = 11.8 MeV)

The study of the angular distribution of electron bremsstrahlung γ-quanta scattered from the reflector surface through an angle of 166 μrad reveals the emergence of total internal reflection of γ quanta with an energy E _γ ≤ 300 keV.     

Geometric analysis of the models of sulfur (S<Subscript>8</Subscript>)<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> molecular nanoclusters in computer experiment

A version of a computer nanoscope is proposed for single crystals with the known atomic structure for a detailed analysis of surface coordination bonds forming on nanosized nuclei due to the intermolecular interaction. Different stages of the study of rhombic and monoclinic sulfur (from the atomic/molecular structure on the first stage to the model packing growth polyhedra on the final stage) are analyzed. The calculation results of the coordination numerical sequences revealed in the computer experiment when the coordination spheres are filled with S₈ molecules with the formation of rather large molecular clusters with a size of about 10 nm or more are presented.     

Frame-like actions for massless mixed-symmetry fields in Minkowski space

A frame-like action for arbitrary mixed-symmetry bosonic massless fields in Minkowski space is constructed. The action is given in a simple form and consists of two terms for a field of any spin. The fields and gauge parameters are certain tensor-valued differential forms. The formulation is based on the unfolded form of equations for mixed-symmetry fields.     

Solution of plane seepage problems for a multivalued seepage law when there is a point source

The steady seepage of an incompressible fluid in a uniform porous medium, occupying an arbitrary bounded two-dimensional region, when there is a point source present is considered. Part of the boundary of the region is free, while the remaining part is impermeable for the fluid. It is assumed that the function defining the seepage law is multivalued and has a linear increase at infinity. A generalized formulation of the problem is proposed in the form of a variational inequality of the second kind. An approximate solution of the problem is obtained by an iterative splitting method, which enables approximate values of both the solution itself (the pressure) and its gradient to be found. Analytic expressions describing the boundaries of the region where the modulus of the pressure gradient takes a constant value are obtained for model problems of a line of bore holes. Numerical experiments are carried out for model problems, which confirm the effectiveness of the proposed method. Good agreement is observed between the results of calculations obtained analytically and by approximate methods.