Infrared rotation-vibration spectra of ethane: The perpendicular band, ν7, of C2H6

The study of the gas-phase infrared spectrum of C₂H₆ in the region of the perpendicular CH-stretching band, ν₇, near 3000 cm^?1 is extended for the ΔK = + 1 subbands as far as K = 20. The spectral resolution of ～0.030 cm^?1 is increased to ～0.015 cm^?1 by deconvolution. The earlier investigation of this band for KΔK = +9 to ?5, is repeated with greater accuracy, providing more reliable ground-state constants (cm^?1): B₀ = 0.663089 ± 24, D₀^J = (0.108 ± 4) × 10^?5, D₀^JK = (0.50 ± 7) × 10^?5. The molecular constants (cm^?1) for the ν₇ fundamental are B₇ = 0.66310 ± 3, A₇ = 2.682, ν₀ = 2985.39, ζ₇ = 0.128. A discussion of resonance effects in this band, in particular x-y-Coriolis and Fermi resonance, is given.     

The absorption cross sections of N2, O2, CO,NO, CO2, N2O,CH4, C2H4, C2H6 and C4H10 from 180 to 700Å

The absorption cross sections of N₂, O₂, CO, NO, CO₂, N₂O, CH₄, C₂H₄, C₂H₆, C₄H₁₀ have been measured photoelectrically in the 180–700 Å region using synchrotron radiation. The absorption cross sections in the region λ ≥ 500 Å was found to be structureless and to increase monotonically with wavelength for all gases. The positions of the structure observed in the 520–720 Å region for N₂, O₂, CO₂ and N₂O are consistent with the various Rydberg series reported by previous authors.     

Interpretation of the ionization spectra of the cyanomethanes: CH3CN,CH2(CN)2 and C(CN)4

The valence ionization spectra of the mono-, di- and tetra-cyanomethane molecules are computed by Green function methods. As previously experienced on other cyano-derivatives of organic molecules, a hole-mixing effect is found. A partial reassignment of the spectrum is possible in the case of CH₂(CN)₂, whereas, due to the compactness of the spectrum and to the limitation of the basis set, an unambiguous assignment is not possible for C(CN)₄. The Koopmans ordering of the IP's is modified in two cases by the many-body perturbation.     

Comparisons of some molecular properties calculated with basis sets of Slater-type orbitals and floating spherical gaussian orbitals for BH3, BH4 -, B2H6, B4H4, C2H2, C2H4, C2H6, CH4, and C3H4

Some one-electron molecular properties are calculated for BH₃, BH₄ ^-, B₂H₆, B₄H₄, CH₄, C₂H₂, C₂H₄, C₂H₆, and C₃H₄. The wave functions used are constructed from minimal basis sets of STO's and FSGO's. The results obtained from the latter wave functions show that the good agreement with the STO values of the molecular energy is not always maintained with one-electron properties.     

Electronic structure and spectra of [Cr(C6H6)2]+ and [Fe(C5H5)2]+

The high-resolution N.M.R. spectra of a series of bicyclo [2.2.1] heptanols are discussed. Three unusual features are observed: (a) relatively large ⁴ J's; (b) unequal J _endo-endo's and J _exo-exo's; and (c) unusual magnetic shieldings.

These are presented as empirical phenomena and only little attempt is made to discuss their implications.     

Fundamental burning velocities of meso-scale propagating spherical flames with H2, CH4 and C3H8 mixtures

This study is performed to experimentally examine the fundamental burning velocity characteristics of meso-scale outwardly propagating spherical laminar flames in the range of flame radius r_f approximately from 1 to 5 mm for hydrogen, methane and propane mixtures, in order to make clear a method for improving combustion of micro–meso scale flames. Macro-scale laminar flames with r_f > 7 mm are also examined for comparison. The mixtures have nearly the same laminar burning velocity (S_L0 = 25 cm/s) for unstretched flames and different equivalence ratios ?. The radius r_f and the burning velocity S_Ll of meso-scale flames are estimated by using sequential schlieren images recorded under appropriate ignition conditions. It is found that S_Ll of hydrogen and methane premixed meso-scale flames at the same r_f or the Karlovitz number Ka shows a tendency to increase with decreasing ?, whereas S_Ll of propane flames increases with ?. However, S_Ll tends to decrease with the Lewis number Le and the Markstein number Ma, irrespective of the type of fuel and ?. It also becomes clear that the optimum flame size and Ka to improve the burning velocity exist for some mixtures depending on Le and fuel types.     

Critical behavior of quasi-2D organic-inorganic halide perovskite (C6H5CH2CH2NH3)2CuCl4 single crystals

Critical behavior of quasi two-dimensional organic-inorganic halide perovskites (C₆H₅CH₂CH₂NH₃)₂CuCl₄ is investigated using magneto-thermal and isothermal magnetic properties along the easy axis. Banerjee's criterion indicates that phase transition from paramagnetic to ferromagnetic phases below T_C = 9.4 K is of second-order. Scaling analysis reveals that critical exponent β from spontaneous magnetization in the critical region below T_C and δ from critical isotherm at T_C are found to be 0.22(3) and 9.28–9.4, close to 2D finite XY model. Meanwhile, γ from magnetic susceptibility in the critical region above T_C is gradually decreased from 2.4 at high-temperature region. Critical exponents from magneto-thermal properties are found to be consistent with those determined from magnetization isotherms. The reliability of critical values is verified using the scaling hypothesis. Our results evidence that (C₆H₅CH₂CH₂NH₃)₂CuCl₄ crossovers from isotropic 2D Heisenberg to anisotropic 3D models towards T_C and can be promising candidates for magnetocaloric materials for hydrogen reliquefaction.     

The microwave spectra of symmetric top polyacetylenes: 1,3,5-Heptatriyne,CH3(CC)3H and 1-cyano-2,4-pentadiyne,CH3(CC)2CN

The rotational spectra of 1,3,5-heptatriyne, CH₃(CC)₃H and 1-cyano-2,4-pentadiyne, CH₃(CC)₂CN have been studied in detail between 26.5 and 40.0 GHz. The molecules have long linear chains of heavy atoms and show characteristic C_3v symmetric top spectra consisting of groups of R-branch lines at regular intervals separated by approximately 2B₀. Six isotopic modifications of CH₃(CC)₂CN have been detected in natural abundance allowing r_s substitution structural data to be derived for this species. Long linear polyacetylenic chains are quite flexible and this dynamic property manifests itself in the appearance of extended sequences of complex vibrational satellites associated with the bending of the chain. The vibrational ground state spectra as well as several low frequency vibrational satellites have been analyzed yielding various vibration-rotation parameters. For CH₃(CC)₃H B₀ = 778.2445 ± 0.0007 and for CH₃(CC)₂CN B₀ = 778.040 ± 0.001 MHz.     

Manifestation of resonance dipole-dipole interaction in spectra of low-temperature molecular mixtures of C2F6 in CF4 and CF4 in C2F6

We have measured IR absorption spectra of solutions C₂F₆ in CF₄ (T = 178 K) and CF₄ in C₂F₆ (T = 173 K) in the overtone range of the spectrum. We have studied how the resonance dipole-dipole interaction affects the formation of contours of bands that correspond to transitions to states involving the vibrations ν₁₀(C₂F₆) and ν₃(CF₄), which are strong in the dipole absorption. For the system C₂F₆ in liquid CF₄, the state ν₂ + ν₁₀(C₂F₆) resonantly interacts with the state ν₂(C₂F₆) + ν₃(CF₄), and, for the system CF₄ in liquid C₂F₆, the state ν₁ + ν₃(CF₄) resonantly interacts with the state ν₁(CF₄) + ν₁₀(C₂F₆). The contours of the bands ν₂ + ν₁₀ (C₂F₆) in the spectrum of the mixture with CF₄ and of the bands ν₁ + ν₃(CF₄) in the spectrum of the mixture with C₂F₆ have been calculated.     

Far-infrared absorption in H2 and H2-HE mixtures

Collision-induced absorption in the translation-rotation band of H₂ and H₂-He mixtures has been measured from 20 to 900 cm^-1 at 77.4, 195 and 292 K. To establish the accuracy of the results, various sources of error are investigated. The zeroth and first spectral moments are evaluated from experiment and theory for H₂ at the various temperatures. To obtain theoretical moments consistent with the experimental values, the quantum pair-distribution function must be used. The major portion of the experimental moments can be accounted for by quadrupole-induced dipoles in H₂ pairs. The remaining portion is attributable to an anistropic overlap interaction, although its magnitude depends on the value of the molecular parameters required to calculate the quadrupole contribution.     

Temperature evolution of the intra-ion absorption spectra of (NH2(C2H5)2)2CoCl4 crystals in the region of their phase transitions

On the basis of spectroscopic studies of (NH₂(C₂H₅)₂)₂CoCl₄ crystals, the absorption bands corresponding to the internal electronic transitions in the Co²⁺ ion were identified. The values of the crystal field and Racah parameters were calculated. The temperature evolution of the absorption spectra of (NH₂(C₂H₅)₂)₂CoCl₄ crystals reveals the anomalies of their parameters at the points of phase transitions. The corresponding changes of the absorption spectra were discussed in terms of distortion of the metal-halogen complex. The temperature dependences of the absorption spectra of (NH₂(C₂H₅)₂)₂CoCl₄ crystals confirm the presence of the thermochromic phase transitions at 255 and 330?K.     

50-5000 eV电子被C4H8O, C5H10O2, C6H5CH3和C4H8O2散射的总截面

使用电子被C, H和O原子散射总截面的实验数据, 利用修正后的可加性规则计算了能量为50-5000 eV的电子被4个复杂大分子C4H8O, C5H10O2, C6H5CH3和C4H8O2散射的总截面, 并将计算结果与实验结果及其他理论计算结果进行了比较. 结果表明, 即使是在几十电子伏的入射能量下, 修正后的可加性规则计算出的总截面依然能与实验结果符合很好, 而使用未修正的可加性规则进行计算, 即使是在几百电子伏的入射能量下得到的总截面仍偏离实验值较远. 分析表明, 未修正的可加性规则计算得到的总截面在中低能区过大、随电子入射能量的增加而衰减太快的问题是由可加性规则本身引起的, 其实质是未考虑低能下分子内原子间的相互屏蔽对散射总截面的计算所带来的影响.     

One- and two-dimensional S=12 Heisenberg antiferromagnetism in Cu(C5H5NO)6 (ClO4)2 and Cu(C5H5NO)6 (BF4)2, respectively

Specific-heat data on CuL₆(ClO₄)₂ and CuL₆(BF₄)₂ in the temperature range 0.05 < T < 20 K are presented (L ≡ C₅H₅NO). The magnetic contributions are found to have the form of broad maxima, occurring near 1 K. Small χ-type anomalies are observed at T_c = 0.62 ± 0.01 K and 0.142 ± 0.002 K for CuL₆(BF₄)₂ and CuL₆(ClO₄)₂, respectively. The analyses show the magnetic structure to be an assembly of weakly coupled antiferromagnetic chains or layers for CuL₆(ClO₄)₂ and CuL₆(BF₄)₂, respectively. For CuL₆(ClO₄)₂ the intrachain exchange constant is J/K = -1.02 ± 0.02 K, for CuL₆(BF₄)₂ the intralayer exchange constant is J/K = -1.10 ± 0.02 K. Additional evidence for the lower-dimensional magnetic structures is obtained from the temperature dependences of the antiferromagnetic susceptibilities. The data on CuL₆(BF₄)₂ clearly indicate the absence of a divergence in the specific heat for the quadratic-layer Heisenberg antiferromagnet, and provide an estimate for the specific heat for this model. A comparison is made with the corresponding result for the ferromagnetic Heisenberg layer.     

1H NMR study of N(CH3)4H(ClF2CCOO)2

The proton spin–lattice relaxation times and ¹H NMR second moments were measured over a wide range of temperature. The results were compared with those of the ¹⁹F NMR relaxation that we obtained earlier. For both nuclear species, the evolution of the longitudinal magnetizations with time is observed to be strongly bi-exponential and were in good quantitative agreement with the cross-relaxation theory.