Low-temperature phase transitions and dynamics of ammonium in (NH4)3H(SO4)2 and [(NH4)1−x Rbx]3H(SO4)2 crystals

The (NH₄)₃H(SO₄)₂ and [(NH₄)_0.82Rb_0.18]₃H(SO₄)₂ crystals are investigated by dielectric spectroscopy, inelastic incoherent neutron scattering (IINS), and neutron powder diffraction. A comparative analysis of the data obtained is given. It is shown that the phase transitions II ? III, III ? IV, IV ? V, and V ? VII in the (NH₄)₃H(SO₄)₂ crystal are accompanied by changes in the orientation ordering of the NH ₄ ⁺ ions. In the [(NH₄)_0.82Rb_0.18]₃H(SO₄)₂ crystal, these phase transitions are completely suppressed and the long-range order inherent in the II phase is retained over the entire temperature range covered (6–300 K). It is revealed that this crystal at the temperature T _g≈70 K undergoes a transition to the dipole glass phase, which is attended by “freezing” the orientation disordering of the ammonium ions.     

Proton conductivity of Al(H2PO4)3–H3PO4 composites at intermediate temperature

Composites of Al(H₂PO₄)₃ and H₃PO₄ were synthesised by soft chemical methods with different Al/P ratios. The Al(H₂PO₄)₃ obtained was found to have a hexagonal symmetry with parameter a = 13.687(3)Å, c = 9.1328(1)Å. The conductivity of this material was measured by a.c. impedance spectroscopy between 100 °C and 200 °C in different atmospheres. The conductivity of pure Al(H₂PO₄)₃ in air is in the order of 10^? 6–10^? 7 S/cm between 100 and 200 °C. For samples containing small excess of H₃PO₄, much higher conductivity was observed. The impedance responses of the composites were found to be similar with AlH₂P₃O₁₀·nH₂O under different relative humidity. The conductivity of Al(H₂PO₄)₃–H₃PO₄ composite with Al/P = 1/3.5 reached 6.6 mS/cm at 200 °C in wet 5% H₂. The extra acid is found to play a key role in enhancing the conductivity of Al(H₂PO₄)₃–H₃PO₄ composite at the surface region of the Al(H₂PO₄)₃ in a core shell type behaviour. 0.7% excess of H₃PO₄ can increase the conductivity by three orders of magnitude. These composites might be alternative electrolytes for intermediate temperature fuel cells and other electrochemical devices. Conductivity (9.5 mS/cm) changed little, when the sample was held at 175 °C for over 100 h as the conductivity stabilised.     

Stereodynamics and Rovibrational Effect for H＋NH3 →H2＋NH2 Reaction

We employ the semirigid vibrating rotor target (SVRT) model to study the influence of rotational and vibrational excitation of the reagent on reactivity for the reaction H NH3. The excitation of the pseudo H-NH2 stretching vibration of the SVRT model gives significant enhancement of reaction probability. Detailed study of the influence of initial rotational states on reaction probability shows strong steric effect. The steric effect of polyatomic reactions, treated by the SVRT model, is more complex and richer than theoretical calculations involving linear molecular models.     

Ab initio Study of Electronic Structure and Magnetic Properties of Two Novel Neptunium （V） Sulfates： iaK3（ipO2）4（SO4）4（H2O）2 and iaipO2SO4H2O

Ab initio within the full potential linearized augmented plane wave （FP-LAPW） method with the GGA＋U approach is applied to study the electronic structures of two compounds NaK3（NpO2）4（SO4）4（H2O）2 and NaNpO2SO4H2O. The present calculations show that the major part of the spin magnetic moment in these two compounds is from Np（V） ions, and the origin of the cation-cation interactions between Np comes from the spin polarization effect within Np-ONv-Np bonds.     

Dissociation and Coulomb Explosion of H2^4＋ in S^q＋ ＋H2 Collisions

We have investigated fragment emission from molecularions in H2^r collisions between S^q and H2 with incident energies of 12.5, 15.625, 18.75, 21.875, 25, 28.125, 31.25, 34.375, 37.5, 40.625, and 43.75 keV/u, respectively. The energy distributions of the fragments are measured by time-of-flight techniques. The experimental results show evidences for molecular Coulomb explosion and dissociation. A program[1] is estab-lished based on the Monte Carlo technique to simulate the time-of-flight spectrum of fragment ions with different initialkinetic energy in ion-Molecule collisions. Simulations are done for S^2 H2 collisions and compared with experimental results.     

Time-resolved spectroscopy and energy transfer in Pr3+-doped Gd2(SO4)3·8H2O

The luminescence of Pr³⁺ in gadolinium sulfate hydrate is reported for 195 nm laser excitation. the Pr³⁺ ion acts as a sensitizer of the host lattice emission. The Pr³⁺Gd³⁺ energy transfer occurs in two different ways. In the octahydrate the transfer occurs from the lowest component of the 4f5d configuration of Pr³⁺, but in the samples with less water there is energy transfer from the¹ S _o level of Pr³⁺ to several Gd³⁺ levels. The Pr³⁺ emission in the two modifications is, of course, also strikingly different.Deceased 24 December 1994     

H3 PAuPh与(H3PAu)2(1,4-C6H4)2光谱性质的密度泛函研究

用密度泛函(DFT)方法优化了配合物H3 PAuPh(a),(H3 Pau)2(1,4-C6 H4)2(b)的基态的几何结构,并用含时密度泛函方法计算了它们的吸收光谱.结果表明配合物a与b的最低能量吸收谱线的波长分别为257.5 nm和307.6nm,皆具有C(2p)→Au(6p)电荷转移参与下的Px(芳环)→px>(芳环)跃迁本质,并伴有Au(5d)→Au(6p)的金属中心电荷转移性质.配合物b是由两个配合物a相连接而成,配合物b的分子轨道也是由配合物a的分子轨道组合而成.由于轨道组合中存在px或Px相互作用,配合物b的最低能量吸收谱线的波长大于配合物a的相应值.     

Proton conductivity in the layer compound H3OUO2AsO4·3H2O (HU As)

The proton conductivity in tetragonal H₃OUO₂AsO₄·(3-)H₂O has been measured above the transition temperature at 299 K. The conductivity, calorimetric and spectroscopic data depend on the water content and the transition is suggested to be a peritectic reaction setting free a small amount of solution, which stays strongly adsorbed between the layers of the structure and gives rise to the high conductivity.     

A study of the ground states of CaC2H2+,CaC2D2+ and CaC2H4+

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Mid-infrared laser-induced grating experiments of C2H4 and NH3 from 0.1–2 MPa and 300–800 K

Laser-induced thermal gratings (LITG) were generated in mixtures of ethylene and ammonia in nitrogen using mid-infrared laser radiation from a grating-tuned, low-pressure, pulsed (5 ms pulse width) CO₂ laser, and read out with a continuous wave Nd:YLF laser. The LITG signal intensity was measured as a function of pressure (0.1–2 MPa) and temperature (300–800 K, at 0.1 and 1 MPa) by tuning the laser to the accidental coincidences of the 10P(14) and 10R(6) emission lines with molecular absorption transitions of C₂H₄ and NH₃, respectively. Comparisons are made with theoretical predictions for the grating efficiency from a simple thermalization model. A theoretical comparison of the temporal LITG signal response for three excitation pulse shapes – a delta function, a realistic pulse, and a square wave is presented. Furthermore, it is shown that for NH₃, most of the decrease of the LITG signal intensity with increasing temperature is due to the corresponding decrease in fractional molecular absorption of the pump beam radiation. The diagnostic capabilities of the mid-infrared LITG experiment is demonstrated for spatially resolved ethylene measurements with long laser pulses in a premixed stoichiometric CH₄–air flame at atmospheric pressure. Received: 17 March 2000 / Revised version: 23 March 2000 / Published online: 13 September 2000     

Structure and magnetotransport properties of the new quasi-two-dimensional molecular metal β″-(BEDT-TTF)4H3O[Fe(C2O4)3] · C6H4Cl2

The β″-(BEDT-TTF)₄A^I[M^III(C₂O₄)₃] · G(A^I=NH ₄ ⁺ , H₃O⁺, K⁺, Rb⁺; M^III=Fe, Cr; G = “guest” solvent molecule) family of layered molecular conductors with magnetic metal oxalate anions exhibits a pronounced dependence of the conducting properties on the type of neutral solvent molecules introduced into the complex anion layer. A new organic dichlorobenzene (C₆H₄Cl₂)-containing conductor of this family, namely, β″-(BEDT-TTF)₄H₃O[Fe(C₂O₄)₃] · C₆H₄Cl₂, is synthesized. The structure of the synthesized single crystals studied by X-ray diffraction is characterized by the following parameters: a = 10.421(1) Å, b= 19.991(2) Å, c= 35.441(3) Å, β = 92.87(1)°, V= 7374(1) ų, space groupC2/c, and Z = 4. In the temperature range 0.5&;2-300 K, the conductivity of the crystals is metallic without changing into a superconducting state. The magnetotransport properties of the crystals are examined in magnetic fields up to 17 T at T = 0.5 K. In fields higher than 10 T, Shubnikov-de Haas oscillations are detected, and the Fourier spectrum of these oscillations contains two frequencies with maximum amplitudes of about 80 and 375 T. The experimental results are compared with the related data obtained for other phases of this family. The possible structural mechanisms of the effect of a guest solvent molecule on the transport properties of the β″-(BEDT-TTF)₄A^I[M^III(C₂O₄)₃] · G crystals are analyzed.     

糖精钴水合物[Co(C7H4NO3S)2(H2O)4]·2H2O的合成及晶体结构

以糖精钠(sac-Na)、丙氨酸和硝酸钴为原料合成得到糖精钴琥珀色块状晶体,采用红外、X射线单晶衍射对配合物进行了表征,该晶体属单斜晶系,空间群为P21/c,晶胞参数为:a=0.79269(5)nm,b=1.61407(10)nm,c=0.77026 (5) nm,α=90°,β=99.695(7)°,Ⅴ=0.97145 (11) nm3,Z=2,Dc=1.817g/cm3,F(000)=546,R=0.0278.结构分析表明,中心Co离子与4个O原子和两个N原子配位,处于四角双锥八面体配位环境中,4个水分子在赤道平面上与Co离子配位,晶胞中还包含有2个游离的结晶水,形成了含6个水分子的结晶物.     

Tensor Force Manifestations in ab Initio Study of the 2H(d, γ)4He, 2H(d, p)3H, and 2H(d, n)3He Reactions

The ²H(d, γ)⁴He capture reaction and the ²H(d, p)³H and ²H(d, n)³He transfer reactions at very low energies are studied in an extended microscopic cluster model with a realistic nucleon–nucleon force. Our results show that the tensor force in realistic interactions plays an essential and indispensable role to reproduce the very low-energy astrophysical S factor of these reactions.     

Tensor force manifestations in ab initio study of the 2H(d,γ)4He, 2H(d,p)3H, and 2H(d,n)3He reactions

The (2)H(d,p)(3)H, (2)H(d,n)(3)He, and (2)H(d,γ)(4)He reactions are studied at low energies in a multichannel ab initio model that takes into account the distortions of the nuclei. The internal wave functions of these nuclei are given by the stochastic variational method with the AV8' realistic interaction and a phenomenological three-body force included to reproduce the two-body thresholds. The obtained astrophysical S factors are all in very good agreement with the experiment. The most important channels for both transfer and radiative capture are identified by comparing to calculations with an effective central force. They are all found to dominate thanks to the tensor force.     

Nuclear Magnetic Resonance Relaxation Study of the Phase Transitions of Rb2CuCl4·2H2O and Cs2MnCl4·2H2O Single Crystals

The physical properties and phase transitions of Rb₂CuCl₄·2H₂O and Cs₂MnCl₄·2H₂O crystals were investigated by performing ⁸⁵Rb, ⁸⁷Rb, and ¹³³Cs nuclear magnetic resonance relaxation analyses. The temperature dependences of the spectra and the spin–lattice relaxation times T ₁ near T _C are related to changes in the symmetry of the octahedrons consisting of four Cl⁻ ions and two water molecules around Rb⁺ or Cs⁺; the forms of these octahedrons are disrupted by the loss of H₂O. The difference between the relaxation times of the two crystals is possibly due to the difference between the electron structures of the Cu and Mn ions. Cu²⁺ has nine valence electrons in its 3d orbital, whereas Mn²⁺ has five valence electrons in its 3d orbital.     

H2-broadening,shifting and mixing coefficients of the doublets in the ν2 and ν4 bands of PH3 at room temperature

The broadening, shifting and mixing coefficients of the doublet spectral lines in the ν₂ and ν₄ bands of PH₃ perturbed by H₂ have been determined at room temperature. Indeed, the collisional spectroscopic parameters: intensities, line widths, line shifts and line mixing parameters, are all grouped together in the collisional relaxation matrix. To analyse the collisional process and physical effects on spectra of phosphine (PH₃), we have used the measurements carried out using a tunable diode-laser spectrometer in the ν₂ and ν₄ bands of PH₃ perturbed by hydrogen (H₂) at room temperature. The recorded spectra are fitted by the Voigt profile and the speed-dependent uncorrelated hard collision model of Rautian and Sobelman. These profiles are developed in the studies of isolated lines and are modified to account for the line mixing effects in the overlapping lines. The line widths, line shifts and line mixing parameters are given for six A₁ and A₂ doublet lines with quantum numbers K = 3n,?(n = 1,?2, …) and overlapped by collisional broadening at pressures of less than 50 mbar.     

(H2O)n (n=1-3)和H2SO4作用下H2CO3气相分解反应机理的理论研究

本文利用CCSD(T)/6-311++(3df,3pd)//B3LYP-D3/6-311++G(3df,3pd)+ 0.9686×ZPE理论方法对(H2O)n (n=1-3)和H2SO4存在与不存在的情况下,H2CO3气相分解反应机理进行了理论研究。计算结果表明(H2O)n (n=1-3)和H2SO4都能使H2CO3气相分解反应的能垒显著地降低,其催化能力按由强到弱的顺序是H2SO4>(H2O)2>(H2O)3>H2O。     

Magnetic circular dichroism and absorption spectra of d° tetrahedral oxyanions and thioanions: MoS4 2-, MoO4 2-, WS4 2-, ReS4 -, VS4 3-, VO4 3- and OsO4

Absorption and magnetic circular dichroism spectra have been measured for the tetrahedral d° ions MoS₄ ^2-, MoO₄ ^2-, WS₄ ^2-, ReS₄ ^-, VS₄ ^3-, VO₄ ^3- and OsO₄ in the visible and ultra-violet spectral range. Comparison of the experimentally obtained MCD parameters with regard to their relative signs leads to the conclusion that probably the first two allowed longest wavelength electronic transitions of all these species have the same assignment (i.e., t ₁ →2e and 3t ₂ →2e, which seems likely on energetic grounds). An estimation of the MCD parameters by using eigenvectors from recently published molecular orbital treatments gave contradictory results.     

超分子化合物C11H6N2O·H3PO4·H2O的合成与晶体结构

采用水热反应法合成超分子化合物C11H6N2O·H3PO4·H2O,通过元素分析、红外光谱和X射线单晶衍射对其组成、结构进行分析.该化合物属于三斜晶系,空间群P-1,晶胞参数a=0.73350(6)nm,b=0.74191(7)nm,c=1.15692(14)nm,α=96.395(2)°,β=92.9940(10)°,γ=90.3440(10)°,V=0.62477(11)nm3,Z=2,F(000)=308,Dc=1.585g·cm-3,最终偏差因子R1=0.0521,wR2=0.1282.该化合物的不对称单元由3个独立的分子4,5-二氮芴-9-酮、磷酸和水分子构成,氢键连接分子形成三维超分子化合物.