Allene nu9 and nu10: Low-Temperature Measurements of Line Intensity

We report laboratory intensity measurements for the weak nu9 (998.8 cm-1) and intense nu10 (841.1 cm-1) bands of allene. Allene is predicted to be a constituent of Titan's atmosphere, and measurements of its abundance would yield important information about the atmospheric chemistry of that body. Spectra were obtained at a temperature of 200 K (approximating Titan conditions) using the high-resolution FTS instrument at Kitt-Peak National Observatory's McMath-Pierce observatory. A total of 505 nu9 and 687 nu10 line intensities were fit using a least-squares method to accurately determine two sets of transition dipole moments. Integrated band intensities computed utilizing the fitted parameters were found to be 36 +/- 4% cm-2 atm-1 and 301 +/- 4% cm-2 atm-1 for nu9 and nu10, respectively, at 200 K. Copyright 1999 Academic Press.     

Infinite Products of Random Isotropically Distributed Matrices

Statistical properties of infinite products of random isotropically distributed matrices are investigated. Both for continuous processes with finite correlation time and discrete sequences of independent matrices, a formalism that allows to calculate easily the Lyapunov spectrum and generalized Lyapunov exponents is developed. This problem is of interest to probability theory, statistical characteristics of matrix T-exponentials are also needed for turbulent transport problems, dynamical chaos and other parts of statistical physics.     

Kinetics of Polymorphous Transformations of Anodic Alumina

Experimental kinetic curves of anodic alumina isothermal transformations in the temperature 800–1200°C are given. The mechanism of transformation and the structure of transformation intermediate and end products are discussed. One-half period curves of monotropic isothermal transformation of amorphous anodic alumina in metastable γ-, δ-, and stable α-phases are given.     

Structure Factors of Sphalerite Crystals with Account of Covalent-Ionic Bond

The derivation and the analysis of structure factor expressions for covalent-ionic sphalerite type A^IIIB^V compounds are given by the parameters of wave-function approximations. Using given expressions the |F_hkl|² values for boron phosphide have been calculated and compared with experimental values. The possibilities of obtaining refined wave functions are indicated.     

Electrooptical Properties of Triglycine Selenate

Materials having noticeable electrooptical properties can be used in different mechanisms for modulation and scanning of light. In this connection a detailed study of the electrooptical effect (EOE) nature and the detection of new materials having electrooptical properties are of great interest. In spite of the fact that the electrooptical properties of triglycine sulphate (TGS) were the subject of research in a number of papers, EOE in isomorphic compounds of TGS has not been studied up till now. The present paper deals with the investigation of the electrooptical effect features in triglycine selenate (TGSe) which represent one of TGS crystallochemical analogues. EOE in TGSe was observed at different directions of the applied electric field: along the ferroelectric axis and perpendicular to it — along OZ. Both longitudinal and transverse electrooptical effects occur in both cases. The features of the temperature variation of longitudinal EOE in TGSe are also considered in this paper.     

Temperature dependence of the X-ray diffuse scattering intensity in V3Si in the temperature range from 8 to 300 K

Measurements of the diffuse X-ray scattering are performed from the (110) plane in V₃Si single crystal at different temperatures from 300 to 8 K. Contours of equal diffuse scattering intensity are drawn over the 440 node in the (001) and (111) sections. The temperature dependence and the anisotropy of the thermal diffuse scattering intensity distribution for this compound are analysed.     

Covalent bonding effect on magnetic susceptibility in AIIIBV semiconductor compounds

On the basis of the expression for magnetic susceptibility of zinc blende semiconductors obtained earlier in the MOLKAO approximation (Sirota, Vitkina) the effect of the degree of covalency on the magnetic suceptibility is studied. The increase of covalency of bonding is shown to be accompanied by the shift of the center of gravity of the charge cloud to the center of bonding and by the increase of the Van Vleck paramagnetic term of the magnetic susceptibility.     

Heat capacity, root-mean-square displacements of atoms and thermal expansion coefficient of europium hexaboride

The temperature dependences of the specific heat capacity c _p(T), thermal expansion coefficient α(T) of europium hexaboride, and root-mean-square displacements of Eu and B atoms are determined in the temperature range from helium to room temperature (5–300 K).     

Stability Determinant of Anisotropic Phases

The thermodynamic stability of crystal determinant D) and nonstability D_{n st}⁽¹⁴) of the fourteenth order, their adiabatic and corresponding isodynamical coefficients are discussed.