Conformational Analysis of 2, 3, 3-Trimethylhexane

Infrared and Raman spectra were obtained for 2, 3, 3-trimethylhexane and were interpreted with the aid of normal coordinate calculations. It was concluded that this compound exists in three molecular conformations, but a fourth conformer may exist. Vibrational assignments were made for the three conformers.     

Modulated magnetic structures of ErPb3, HoPb3, ErTl3 and HoTl3

Neutron diffraction experiments have been carried out on the magnetically ordered phases of ErPb₃, HoPb₃, ErTl₃ and HoTl₃. The magnetic moments were found to be sinusoidally modulated with a propagation vector of (0, 0.2, 0.5) for the Pb-compounds and (0.38, 0.38, 0.16) for the Tl-compounds.Work supported by the Bundesministerium für Forschung und Technologie     

Far infrared optical properties of polycrystalline NaClO3, KClO3, NaBrO3 and KBrO3

The resonant frequencies, damping constants and oscillator strengths of far infrared lattice vibrations of polycrystalline NaClO₃, KClO₃, NaBrO₃ and KBrO₃ have been obtained through classical dispersion (CD) analysis of transmission data. Space group analysis has been applied for attribution assignments and to ascertain the translational and rotational character of the respective lattice bands. The damping constants were found to be unusually large indicating short lifetimes of the excited states in spite of an apparent absence of phonon-phonon coupling. The CD analysis of the spectra also provide reliable values of oscillator strength and resonant frequency.     

Dipole properties of PH3, PF3, PF5, PCl3, SiCl4, GeCl4, and SnCl4

Experimental and theoretical photoabsorption cross sections combined with constraints provided by the Kuhn–Reiche–Thomas sum rule, the high-energy behaviour of the dipole oscillator strength density, static dipole polarisabilities, and molar refractivity data when available are used to construct dipole oscillator strength distributions for PH₃, PF₃, PF₅, PCl₃, SiCl₄, GeCl₄, and SnCl₄. The distributions are used to predict dipole sum rules S(k), mean excitation energies I(k), and van der Waals C₆ coefficients.     

Infrared spectra of matrix isolated BH3NH3, BD3ND3, and BH3ND3

The infrared spectra of ammonia-borane, BH₃NH₃, and two of its deuterated isotropic species, BD₃ND₃ and BH₃ND₃, isolated in argon matrix at liquid hydrogen temperature have been measured. Well resolved bands for these three isotopic species have been observed for all the fundamentals. A complete frequency assignment based on C₃v molecular symmetry has been made. A set of force constants have been calculated from the data for the two isotopes BH₃NH₃ and BD₃ND₃ using a valence force field. The agreement between experiment and frequencies calculated from these force constants for the mixed isotopic species, BH₃ND₃, substantiates the present assignment.     

Slow-electron excitation of 3 S, 3 P, and 3 P 0 levels of the strontium atom

The electron impact excitation of ³ S, ³ P, and ³ P ⁰ levels of atomic strontium was investigated by the methods of extended crossed beams and optical spectroscopy. The results obtained are compared with the data of the previous experiment and the theoretical results. The behavior of excitation cross sections in spectral series of SrI is discussed.     

Relation between electrooptical constants and polar tensors of CH3F,CD3F,CH3Cl,CD3Cl,CH3Br,CD3Br,CD3I,and CD3I

Infrared intensity analysis was done in two ways. In one approach, formulas connecting electrooptical parameters (eop's) and intensities were derived and, using the intensities, the former were obtained. In evaluating the eop's the intensity sum equations were used directly so that the sign ambiguity of $\text{δP}\text{δQ}$ is avoided. In the other method, polar tensors were obtained directly from intensities. The two methods have now been connected, and polar tensors have been obtained in terms of electrooptical parameters so that the former were also free from sign ambiguity of $\text{δP}\text{δQ}$. They compare well with those obtained directly from intensities. In similar connecting formulas by other authors [see, for example, P. L. Prasad, J. Chem. Phys., 69, 4403, (1978)], both polar tensors and eop's were affected by the sign ambiguity.     

Infrared rotation-vibration spectra of ethane: The parallel band, 2ν3, of CH3CD3

The parallel band, 2ν₃, of CH₃CD₃ is measured in the region 2715 to 2780 cm^?1 under a spectral resolution of ～0.025 cm^?1, increased to ～0.015 cm^?1 by deconvolution. About 460 lines are identified in the 2ν₃ band, and about 240 lines in a hot band arising from the first excited torsional state. Least-squares analyses with Δ₂F″ combination differences yield lower-state parameters. An individual subband analysis is undertaken because of perturbations in the vibrational bands studied. Finally, band constants are derived.     

Sphere packing, helices and the polytope {3, 3, 5}

The packing of tetrahedra in face contact is well-known to be relevant to atomic clustering in many complex alloys. We briefly review some of the structures that can arise in this way, and introduce methods of dealing with the geometry of the polytope {3, 3, 5}, which is highly relevant to an understanding of these structures. Finally, we present a method of projection from S₃ to E₃ that enables coordinates for the key vertices of the collagen model of Sadoc and Rivier to be calculated. Received 27 March 2001     

High pressure transport characteristics of Bi2Te3, Sb2Te3, and BiSbTe3

This paper presents ambient and high pressure measurements of transport properties of the Bi₂Te₃–Sb₂Te₃ series of materials. The electrical resistivity, thermal conductivity, and Seebeck coefficient have been measured on both end compounds and the direct solid solution of the two at pressure up to 10 GPa. An additional discussion involving the high pressure structure will be presented. From this, it was determined that these materials undergo at least two structural phase transitions between 0 and 20 GPa and a discussion is presented regarding this and the changes in the transport properties.     

The Features of Low-Lying States of Ne3, Ar3 and Kr3

The methods for few-body physics are introduced to extract structures of low-lying states of threeatom clusters of neon, argon and krypton. Similarities among the states have been found, and accordingly a number of rotational bands have been identified. Each band is characterized by a specific mode of internal oscillation. The decisive effect of symmetry has been emphasized.     

Electrical and thermal conductivity of CePd3, YPd3, GdPd3 and some dilute alloys of CePd3 with Y and Gd

Resistivity and thermal conductivity of the intermediate valence compound CePd₃ between 1.3 and 300 K are compared with those of the nonmagnetic and magnetic reference compounds YPd₃ and GdPd₃ and of alloys of the type Ce₁–xRE _x Pd₃ with RE=Y, Gd and 0.01<x<0.5. The analysis reveals the existence of a maximum metallic resistivity of 300 cm for CePd₃. The intrinsic resistivity of CePd₃ rises proportional toT ² up to 100 K, with a coefficientB about 10⁷ times larger than e.g. in copper. We interpret this with indirect electron-electron scattering mediated through valence transitions.     

Triple differential cross section of electron impact ionisation of Na(3s, 3p, 3d)

The fivefold differential cross section (5DCS) of the ionisation by electron impact of atomic sodium is determined theoretically for its fundamental 3s(² S) state and the excited 3p(² P) and 3d(² D) states by a procedure which employs in the transition matrix element of the first order Born approximation, the correlated double continuum (3C) wave function. This permits us to determine the statistical M-state population and the orientation and alignment tensors in (e,2e) detection. It is also shown that, the use of Gamow correlation term, in the independent particle (2C) model, reproduces, only in some situations, the shape of the angular distribution of the 5DCS obtained by the (3C) wave function. Received: 17 November 1997 / Received in final form: 16 March 1998 / Accepted: 21 March 1998     

Li3N、Mg3N2、Ca3N2催化作用的比较和分析

 Li₃N、Mg₃N₂和Ca₃N₂是高温高压下以hBN为原料合成cBN的催化剂。在实验中发现它们对常压高温下生成hBN的反应也表现出催化作用。对比了三种氮化物催化效果的差异，发现三种氮化物都只有在熔融状态下才能表现出催化效果，以及三种氮化物对生成hBN反应的催化效果与它们在高温高压下合成cBN反应的催化效果次序相似。提出了对合成hBN有催化作用的化合物也将对合成cBN表现出催化作用的观点。     

The vapour phase Raman spectra,Raman band contour analyses,Coriolis coupling constants,and e-species force constants for the molecules HCF3, ClCF3, BrCF3, and ICF3

The vapour phase Raman spectra of the molecules HCF₃, ClCF₃, BrCF₃, and ICF₃ have been recorded at pressures of up to 1 atmosphere over the fundamental frequency regions. The Raman band contours of the e-species fundamentals have been analysed to yield first-order Coriolis coupling constants from which, together with the fundamental frequencies, e-species force constants of the general harmonic potential function have been evaluated. One force field was found for fluoroform, but two different ones were found for the molecules ClCF₃, BrCF₃ and ICF₃.