Effect of the internal rotation of the CHD2 group on the CH stretching infrared and Raman spectra of toluene C6D5CHD2 and nitromethane NO2CHD2 in vapor phase

Gas-phase infrared and Raman spectra of toluene C₆D₅CHD₂ and nitromethane NO₂CHD₂ were recorded in the CH stretching region. They are all characterized by a strong band with a weaker one at lower frequency. These bands have simple Raman profiles and their infrared contours are respectively of A and C type. A quantum theory of these spectra is put forward, assuming an anharmonic coupling of the νCH mode with the internal rotation of the CHD₂ group in the adiabatic approximation. Theoretical calculations based on this model give a good fit of the experimental Raman bandshapes and a good picture of the observed infrared spectra. Thus each of the observed bands can be characterized. The frequency of the intense band is the average of that of the νCH mode during the almost free internal rotation of the CHD₂ group, while the frequency of the weaker band is approximately equal to the minimal νCH frequency. This last one corresponds to the position of the CH bond in a plane perpendicular to that of the molecule (ν_⊥CH). The frequency difference between ν_∥CH (the CH bond being in the plane of the molecule) and ν_⊥CH is found to be 42 cm^?1 for the two compounds.     

Vibrational spectra of nitromethanes and the effects of internal rotation

Infrared spectra have been obtained in gas and crystalline phases for CH₃NO₂, CD₃NO₂, and CHD₂NO₂. A few Raman liquid measurements have also been made. The crystal spectra show the methyl group to be locked in conformation I,

with isolated CH stretching frequencies 3065 (ν_∥CH) and 3000 (ν_⊥CH), respectively. In the gas phase, the bands due to ν_aCH₃ and ν_aCD₃ are split, the splitting being compatible with isolated frequencies of 3065 (ν_∥CH) and 3006 (ν_⊥CH) cm^?1, respectively. These indicate a variation of 0.006 Å in bond length during internal rotation. The gas phase infrared band at 3028.7 cm^?1 and the Raman liquid band at 3024 cm^?1 in the spectra of CHD₂NO₂ represent averages of the frequencies during internal rotation. All calculations are performed with a potential function involving variations both in diagonal bond stretching, and in off-diagonal stretching interaction constants, proportional to cos2π, where π is the internal rotation angle.In the Appendix, vibrational assignments below 1600 cm^?1 are examined. Product rule considerations and intensity changes upon deuteration lead to a conflict with the infrared gas phase band contour over the assignment of the rCD₃ mode at 884 cm^?1. This and other features in the gas phase spectra may arise from the internal rotation.     

A specific heat study of the nematic-smectic-A transition in octyloxycyanobiphenyl

A high-resolution ac calorimetry measurement of the nematic to smectic-A transition has been carried out carefully on octyloxycyanobiphenyl (80CB). The measured critical exponents α = α′ = .24 ± .03 are consistent with X-ray results through the hyperscaling relation ν∥ + 2ν_⊥ = 2 - α.     

On anomalies of anisotropic thermal expansion near points of electronic topological transitions in noncubic metals. Applications to Zn,Cd and CdMg alloys

Singularities of the low-temperature coefficients of the thermal expansion, α_i(T), near points of electronic topological transitions (ETT) in noncubic metals are investigated. Using a uniaxial metal with a weak pseudopotential of the electron-ion interaction as an example, it is shown that the longitudinal α_∥ and transverse α_⊥ coefficients should be opposite in sign near the ETT point, while the ∥α_i∥ values can considerably exceed the volume coefficient β=α_∥ + 2α_⊥. These conclusions are illustrated by ab initio band structure calculations for the hcp Zn, Cd and CdMg alloys. The results explain the scale and sign of the α_i low-temperature anomalies in Zn and Cd (α_∥ > 0, α_⊥ < 0>). For the Cd_1-xMg_x alloys the anomaly inversion (α_∥ < 0, α_⊥ > 0) is predicted after the first ETT at the point x=x_c1≈0.06, as well as its sharp growth (the ∥α_i∥ increase) after the second ETT at x_c2≈0.12.     

A spectroscopic study of water vapor isotopologues H2O, H2O and HDO using a continuous wave DFB quantum cascade laser in the 6.7 μm region for atmospheric applications

A quantum cascade spectrometer was used in the laboratory to study H₂¹⁶O, H₂¹⁸O and HDO line intensities near 6.7 μm. The spectral region ranging from 1483 to 1487 cm⁻¹, which is suitable for the in situ laser sensing of these isotopologues in the atmosphere, was investigated using a continuous-wave distributed feed-back quantum cascade laser. Eight lines of water vapor isopologues were studied—one line of the ν₂ band of H₂¹⁶O, one line of the 2ν₂-ν₂ band of H₂¹⁶O, two lines of the ν₂ band of H₂¹⁸O and four lines of the ν₂ band of HDO were carefully revisited. The measured intensities were thoroughly compared to relevant molecular databases and other experimental and calculated results. We also observe that the H₂O, D₂O, HDO equilibrium constant agrees excellently with previously determined values.     

Thermoreflectance of single crystal Gd

Thermoreflectance spectra for E∥c and E⊥c were measured on a Gd single crystal. The thermoconductance spectra, Δσ_∥ and Δσ_t], are very anisotropic. The strong interband edge at about 0.5 eV is shown to arise from a transition to or from the Fermi level for E⊥c. For E∥c additional effects occur.     

Low temperature ESR of K2Pt(CN)4Br0.3. 3.2 H2O

Electron spin resonance has been observed in high purity single crystals of K₂Pt(CN)₄Br_0.3·3.2H₂O, (KCP), in the temperature range of 4.22–80 K. Two types of paramagnetic species are found to dominate the spectrum. One of these is an inhomogeneously broadened line showing no resolved hyperfine splitting and having g_∥ = 1.946 ± 0.003 and g⊥ = 2.340 ± 0.003. The second paramagnet is identified as a Cu²⁺ impurity center with g_∥ = 2.231 ± 0.003, g⊥ = 2.079 ± 0.002 and hyperfine tensor A_∥ = 467 MHz, A_⊥ = 70 MHz.     

Exact solution for the extended Debye theory of dielectric relaxation of nematic liquid crystals

The exact solution for the transverse (i.e. in the direction perpendicular to the director axis) component α_⊥(ω) of a nematic liquid crystal and the corresponding correlation time T_⊥ is presented for the uniaxial potential of Martin et al. [Symp. Faraday Soc. 5 (1971) 119]. The corresponding longitudinal (i.e. parallel to the director axis) quantities α_⊥(ω), T_⊥ may be determined by simply replacing magnetic quantities by the corresponding electric ones in our previous study of the magnetic relaxation of single domain ferromagnetic particles Coffey et al. [Phys. Rev. E 49 (1994) 1869]. The calculation of α_⊥(ω) is accomplished by expanding the spatial part of the distribution function of permanent dipole moment orientations on the unit sphere in the Fokker-Planck equation in normalised spherical harmonics. This leads to a three term recurrence relation for the Laplace transform of the transverse decay functions. The recurrence relation is solved exactly in terms of continued fractions. The zero frequency limit of the solution yields an analytic formula for the transverse correlation time T_⊥ which is easily tabulated for all nematic potential barrier heights σ. A simple analytic expression for T_∥ which consists of the well known Meier-Saupe formula [Mol. Cryst. 1 (1966) 515] with a substantial correction term which yields a close approximation to the exact solution for all σ, and the correct asymptotic behaviour, is also given. The effective eigenvalue method is shown to yield a simple formula for T_⊥ which is valid for all σ. It appears that the low frequency relaxation process for both orientations of the applied field is accurately described in each case by a single Debye type mechanism with corresponding relaxation times (T_∥, T_⊥).     

The 4 A 2→2 E transitions of 2[Cr(en)3Cl3]KCl. 6H2O in strong magnetic fields

The Zeeman effect of the R absorption lines for the pure compound 2[Cr(en)₃Cl₃]KCl.6H₂O has been measured photographically, using a strong pulsed magnet with fields of up to 200 000 gauss at 77 K. The results indicate g _∥ (⁴ A ₂) = 1·82 , g _⊥(⁴ A ₂) = 1·90 with g _∥(ē) = -1·82 and g _∥ (2ā) = 1·82. The uncertainties are of the order of ± 0·05.     

Two mutually-repelling self-avoiding walks: A Monte Carlo study

We consider two self-avoiding walks (SAWs) on a square lattice, beginning simultaneously from two arbitrary nearest neighbours. The walks cross neither themselves nor each other, and grow simultaneously. Using Monte Carlo technique we study the variation, with the length N of the walks, of the average end-to-end distance 〈R_N〉 of each walk and of their average separation 〈S_N〉. We find 〈R_N²〉∞N^2ν, 〈S_N²〉∞N^2λ, where ν ≈ λ ≈ 0.75 for two ordinary SAWs and ν ≈ λ ≈ 0.67 for two growing SAWs in two dimensions. For two directed SAWs, we find 〈R_N∥/⊥²〉 ∞ N^2ν∥/⊥ and 〈S_N∥/⊥² 〉 ∞ N^2λ_∥/⊥, where ν_∥ ≈ 1.00, ν_⊥ ≈ 0.56, λ_∥ ≈ 0.50 and λ_⊥ ≈ 0.59 in two dimensions. We thus find an indirect excluded volume effect on one directed SAW, due to the other.     

Constraints fulfilled by density moments and density correlations

The first set of equations we are going to consider follow from the conservation of additive quantum numbers. These constraints assume a simpler form than the corresponding relations for inclusive cross sections and inclusive correlations and can all be fulfilled consistently with any collection of higher order density correlation functions G_ms(x,k_⊥1,ν₁,…, x_m, k_⊥m,ν_m), m ≥ 2, identically zero. We will also derive a set of constraints from the requirements that the probability of any particular class of final states must be a number greater than or equal to zero, and the number of particles of certain type which appear in any region of momentum space must also be positive of zero. These relations can be fulfilled with any finite sequence of density correlations G_ms(x₁, k_⊥1,ν₁,…, x_m, k_⊥m, ν_m), m ≥ 3, identically equal to zero, or with all correlations of order m ≥ 2 identically zero.     

Discovery of multiple bands of isotopic CO2 in the prime spectral regions used when searching for CH4 and HDO on Mars

We present new measurements of vibrational band systems of isotopic carbon dioxide (CO₂) with multiple strong lines in the wavelength region 3.3-3.7 μm. In our ground-based searches for methane (CH₄) and other biomarker gases on Mars, we discovered two new vibrational band systems that we identify as the previously unknown ν₂+ν₃ band of ¹⁶O¹²C¹⁸O and the 2ν₁ band of the rare isotope ¹⁶O¹³C¹⁸O. We also extended and provide refined spectroscopic constants for the 2ν₁ band of ¹⁶O¹²C¹⁷O, detecting 38 new lines. The newly discovered 2ν₁ band of ¹⁶O¹³C¹⁸O at 3.7 μm and the 2ν₁ band of ¹⁶O¹²C¹⁷O at 3.6 μm extend over the prime spectral region used when searching for deuterated water (HDO) and formaldehyde (H₂CO) on Mars. The ν₂+ν₃ band of ¹⁶O¹²C¹⁸O at 3.3 μm interferes with the ν₃ band of CH₄ at 3.3 μm. If unrecognized, even weak bands of CO₂ can obscure searches for trace gases on Mars, so it is important to quantify them. Here, we report molecular parameters from the measured line positions that agree well with values calculated from the known energy levels of these isotopologues, and we provide absolute band strengths for each system.     

The anomalous quasi isotropic [g] tensor found for CdBr2:Ag2+ and AgBr0.15Cl0.85:Ag2+: An explanation through strong covalency

The “anomalous” quasi-isotropic [g] tensor observed in systems containing the elongated AgBr⁴⁻₆ unit (g_∥ = 2.078 ± 0.003; g⊥ = 2.065 ± 0.003) is reasonably explained, within a rigorous Molecular Orbital framework, in terms of a very high covalency, consistent with the optical electronegativity of Ag²⁺ and previous results on other Cu²⁺ and Ag²⁺ complexes. For the antibonding level 3b_1g(x² − y²) about 90% of the electronic charges should be on bromine ions. The present analysis reveals that g_∥ − g₀ is dominated by charge-transfer excitations while g_⊥− g₀ is dominated by crystal-field excitations.     

Waves in a superlattice with anisotropic inhomogeneities

Dependences of the dispersion laws and damping of waves in an initially sinusoidal superlattice on inhomogeneities with anisotropic correlation properties are studied for the first time. The period of the superlattice is modulated by the random function described by the anisotropic correlation function K_?(r) that has different correlation radii, k _∥ ^?1 and k _⊥ ^?1 , along the axis of the superlattice z and in the plane xy, respectively. The anisotropy of the correlation is characterized by the parameter λ=1?k_⊥/k_∥ that can change from λ=0 to λ=1 when the correlation wave number k⊥ changes from k_⊥=k_∥ (isotropic 3D inhomogeneities) to k_⊥=0 (1D inhomogeneities). The correlation function of the superlattice K(r) is developed. Its decreasing part goes to the asymptote L that divides the correlation volume into two parts, characterized by finite and infinite correlation radii. The dependences of the width of the gap in the spectrum at the boundary of the Brillouin zone δν and the damping of waves ξ on the value of λ are studied. It is shown that decreasing L leads to the decrease of δν, and increase of ξ, with the increase of λ.     

关于辐射在双麦克斯韦等离子体中散射的结构因子

文献[1]在计算双麦克斯韦等离子体的辐射散射结构因子的时候,区分T_⊥≥T_∥和T_⊥≤T_∥两种情况,得到两个不同形式的解析表达式。本文指出,区分这两种情况是没有必要的,可以得到具有更高精确度的统一解析表达式。 关键词：     

Infrared and laser Raman gas spectra of SnH4

In the present work the ν₃(f₂) Raman band and the 2ν₃ infrared band of SnH₄ are reported. Analyses have been performed for the ν₃(f₂) Raman band and the ν₂(e), ν₃(f₂), ν₄(f₂) and 2ν₃ infrared bands. The interatomic distance in the ground state has been found to be 1.7108 ± 0.0010 Å.     

Cyclotron resonance studies on bulk and two-dimensional conduction electrons in InSe

Cyclotron resonance is reported for both bulk electrons and electrons bound to charged defect planes in the layer compound InSe. At temperatures below 20 K all carriers present are bound to defect planes and behave as two-dimensional accumulation layers. At higher temperatures the electrons are excited into bulk regions between the defects, and show three-dimensional, bulk behaviour. The conduction band is shown to exhibit an “anomalous anisotropy” with m_∥ = 0.08m₀ and m_⊥ = 0.14m₀. The bound, two-dimensional carriers exhibit a strong non-parabolicity, and show a band edge mass m_⊥ = 0.13 which is considerably lower than the bulk value possibly due to a reduction in the polaron constant in the degenerate electron gas.     

Contribution to the study of the 2ν5 (A1) rovibrational band of CH3Br near 2860 cm−1

This band was studied on a Fourier Transform spectrum (resolving power of the apparatus: 0.005 cm^?1). For each isotopic species CH₃⁷⁹Br and CH₃⁸¹Br, about 800 lines were assigned. The band is well explained by a x-y type Coriolis interaction with ν₂ + ν₅. Several local resonances occur for low K values as well as a doubling of the K = 3 levels. Their study provides interesting information on neighboring bands, especially 3ν₆(E), ν₂ + ν₃ + ν₆, and 2ν₅(E).     

Effect of the spin-orbit interaction of Ni2+ ions with a triplet orbital ground state on the magnetostriction of NiFe0.5Cr1.5O4 ferrite

The magnetization σ and the longitudinal (λ_∥) and transverse (λ_⊥) magnetostrictions of the NiFe_0.5Cr_1.5O₄ ferrite containing the tetrahedral ions Ni²⁺ with the triplet orbital ground state have been investigated for the first time at a temperature of 4.2 K in fields up to 55 kOe. It is revealed that the NiFe_0.5Cr_1.5O₄ ferrite exhibits an anomalously large magnetic anisotropy (H _c=12.5 kOe) and magnetostrictions (λ_∥≈?870×10^?6 and λ_⊥≈800×10^?6). In strong fields, the magnetostrictions λ_∥ and λ_⊥ are found to be anisotropic in character; i.e., the susceptibility Δλ_∥p and Δλ_⊥p. The conclusion is drawn that the studied compound is characterized by two paraprocesses: one paraprocess in the B sublattice has an exchange nature, and the second process in the A sublattice is due to the spin-orbit interaction of Ni _A ²⁺ ions.     

SO2: High-resolution analysis of the (0 3 0), (1 0 1), (1 1 1), (0 0 2) and (2 0 1) vibrational states; determination of equilibrium rotational constants for sulfur dioxide and anharmonic vibrational constants

High resolution Fourier transform spectra of a sample of sulfur dioxide, enriched in ³⁴S (95.3%). were completely analyzed leading to a large set of assigned lines. The experimental levels derived from this set of transitions were fit to within their experimental uncertainties using Watson-type Hamiltonians. Precise band centers, rotational and centrifugal distortion constants were determined. The following band centers in cm⁻¹ were obtained: ν₀(3ν₂)=1538.720198(11), ν₀(ν₁ + ν₃)=2475.828004(29), ν₀(ν₁ + ν₂ + ν₃)=2982.118600(20), ν₀(2ν₃)=2679.800919(35), and ν₀(2ν₁ + ν₃)=3598.773915(38). The rotational constants obtained in this work have been fit together with the rotational constants of lower-lying vibrational states [W.J. Lafferty, J.-M. Flaud, R.L. Sams, EL Hadjiabib, J. Mol. Spectrosc. 252 (2008) 72-76] to obtain equilibrium constants as well as vibration-rotation constants. These equilibrium constants have been fit together with those of ³²S¹⁶O₂ [J.-M. Flaud, W.J. Lafferty, J. Mol. Spectrosc. 16 (1993) 396-402] leading to an improved equilibrium structure. Finally the observed band centers have been fit to obtain anharmonic rotational constants.