The measurement of pressure-induced shifts of the J = 0 → 1 transition of CH3Cl35 at various temperatures

Temperature behavior of the rotational resonance (J = 0 → 1, F = 3/2→5/2) transition of CH₃Cl³⁵ under various pressures was investigated over a range of 193 ≤ T ≤ 366K using a source-modulated spectrometer to ascertain how the central resonance shifted as the perturbing gas pressure within the absorption cell was varied. Frequency shifts were determined for measured pressures of 1 ≤ P ≤ 30mTorr for the temperature range specified. Experimental results are compared with recent theoretical calculations.     

Pressure broadening of the NH3 pure rotation line (JI = 0 → JF = 1) perturbed by inert gases (He,Ne, Ar,Kr)

We have calculated the linewidths of the NH₃ pure rotation line (J_I = 0 → J_F = 1) perturbed by inert gases (He, Ne, Ar, Kr) using a convergent impact theory. We have taken into account the dipole-induced dipole, quadrupole-induced dipole and dispersion terms of Krishnaji and Prakash and the dispersion term of Tipping and Herman. Our theoretical results and those obtained with the Anderson and Tsao and Curnette theory are compared with experimental results.     

Magnetic susceptibilities of polycrystalline samples of the compounds ANiCl3 (A = RB,NH4, Tl,Cs) and ANiBr3 (A = Rb,Cs)

The susceptibilities of polycrystalline samples of various antiferromagnetic linear-chain compounds ANiX₃ (A =Tl, NH₄, Rb, Cs and X = Cl, Br) have been measured in the temperature region 2–200 °K. The results, amongst which the already known data for RbNiCl₃ and CsNiCl₃, are interpreted in terms of a theory, developed by Weng, for antiferromagnetic Heisenberg linear-chain systems with spin S = 1. By means of Oguchi's Green function theory and the experimentally determined transition temperatures T_N the order of magnitude of the ratio between inter- and intra-chain interaction is obtained.     

On the relaxation rates determining the NH3 and ND3 inversion spectra

A general approach towards the calculation of relaxation rates in the semiclassical approximation is described and applied to a discussion of the NH₃ and ND₃ inversion spectra.     

Rotational analysis and radiative lifetime measurement on the 2B1 (K′ = 0) excited state of NO2 with v′2 = 6, 7, 8, and 9

The rotational structure of the ²B₁ (K′ = 0) subbands of NO₂ with v′₂ = 6, 7, 8, and 9 were analyzed by means of the time-gated excitation spectrum. The excitation spectrum monitored at ν₂, 2ν₂, or 3ν₂ fluorescence band was fairly simplified in comparison to its corresponding absorption spectrum. The band origins and rotational constants are evaluated from the observed data: ν₀ = 20205.0 cm^?1, $\text{B}\text{′ = 0.374}\text{cm}{}^{\mathrm{?1}}$ for v′₂ = 6; ν₀ = 21104.4 cm^?1, $\text{B}\text{′ = 0.374}\text{cm}{}^{\mathrm{?1}}$ for v′₂ = 7; ν₀ = 22001.9 cm^?1, $\text{B}\text{′ = 0.375}\text{cm}{}^{\mathrm{?1}}$ for v′₂ = 8ν₀ = 22898.0 cm^?1, $\text{B}\text{′ = 0.375}\text{cm}{}^{\mathrm{?1}}$ for v′₂ = 9. The value of $\text{B}\text{′}$ extrapolated to v′ = 0 is 0.370 cm^?1. This value corresponds to the bond length of 1.19 Å. Fluorescence decays of these excited levels were also studied. Radiative lifetimes obtained by extrapolation to zero pressure from the $\text{1}\text{τ}\text{– P}$ plots were 25–40 μsec. The short-lived excited levels previously reported by some authors were not found.     

Vibrational anharmonicity and the inversion potential function of NH3

The nonrigid bender formulation of the vibration-inversion-rotation Hamiltonian for an XY₃ pyramidal molecule (V. ?pirko, J. M. R. Stone, and D. Papou?ek, J. Mol. Spectrosc.60, 159 (1976)) is improved by allowing for anharmonicity in all the vibrations. To model the anharmonic potential function of an XY₃ molecule with a low barrier to inversion a Plíva-type empirical potential (J. Plíva, Collect. Czech. Chem. Commun.23, 777 (1958)) is used. A fitting procedure that involves the numerical integration of the effective inversion Schrödinger equation (the nonrigid bender equation) and diagonalization of some resonance matrices is used to determine the equilibrium structure and the anharmonic potential function of the ammonia molecule.     

The energetics of NH3 adsorption at the MgO(001) surface

Ab initio quantum-mechanical calculations based on density-functional theory and the pseudopotential method have been used to study the adsorption of the NH₃ molecule at the MgO(001) surface. The calculations employ slab geometry and periodic boundary conditions, with the occupied orbitals expanded in plane waves. The reliability of the theoretical methods has been verified by calculations on the bare surface and the isolated molecule. Four different adsorption geometries have been studied, and in each case the equilibrium configuration has been determined by full relaxation of the system. The two most stable configurations have about the same adsorption energy, and this energy agrees well with the results of recent thermal desorption measurements. Intermolecular repulsion is found to be a dominant effect at monolayer coverage, but becomes small at coverages below 25%. It is shown that chemical effects are not significant, and that the adsorption mechanism is predominantly physisorption.     

(NH4)2SO4，NH4NO3和(NH4)2SO4/NH4NO3混合气溶胶吸湿质量增长因子的快速测量方法

气溶胶颗粒的吸湿性决定了其尺寸、浓度、化学组成以及相态,从而显著影响着全球气候、大气异相化学以及人类健康。运用在线、原位、连续扫描衰减全反射傅里叶变换红外光谱（ATR-FTIR）技术, 结合线性湿度（RH）控制系统,实现了RH连续变化条件下气溶胶FTIR-ATR光谱的快速测量。根据水弯曲振动谱带（~1 640 cm-1）峰面积随RH的变化,得到了(NH₄)₂SO₄,NH₄NO₃和(NH₄)₂SO₄/NH₄NO₃混合气溶胶的质量增长因子（MGFs）、潮解点（DRH）和风化点（ERH）。与气溶胶的E-AIM模型预测值相比较,实验结果表现出良好的一致性,证实该方法是一种测量大气气溶胶MGFs,ERH和DRH的快速测量方法。     

NMR spectral densities and two dimensional diffusion in TiS2(NH3)1.0 and TaS2(NH3)x

NMR measurements of proton spin-lattice relaxation times T₁ and T_1? in the layered intercalation compounds TiS₂(NH₃)_1.0 and TaS₂(NH₃)_x (x = 0.8, 0.9, 1.0) are reported as functions of frequency and temperature (100 K – 300 K). These observations probe the spectral density of magnetic fluctuations due to motions of the intercalated molecules at frequencies accessible to the T₁ (4–90 MHz) and T_1? (1–100 kHz) measurements. Since the average molecular hopping time (τ) can be changed by varying temperature, different regions of the spectral density can be examined. For T > 200 K, both T^?1₁ and T^?1_1? vary logarithmically with frequency, reflecting the two dimensional character of the molecular diffusion. The temperature dependence of T₁ suggests that a more accurate picture of the short time dynamics is required. No dependence of relaxation rate on vacancy concentration is found.     

Chemical shifts of copper and cobalt K absorption discontinuities in the spinels CuCr2X4 (X =O,S, Se,Te), CoCr2X4 (X =O,S) and Cu0.5Co0.5Cr2−xRhxS4 (x = 0, 1, 2)

The present paper reports the chemical shifts of the copper and cobalt K absorption discontinuities in the spinels CuCr₂X₄ (X = O, S, Se, Te), CoCr₂X₄ (X = O, S) and Cu_0.5Co_0.5Cr_2?xRh_xS₄ (x = 0, 1, 2). The magnitudes of the chemical shifts show that copper is monovalent (except in CuCr₂O₄) and cobalt is bivalent in all these spinels. The valence structure for the spinels containing copper shows that the conductivity of such spinels (except CuCr₂O₄) is due to the holes in the anion p-orbitals. Levine's theory of ionicity has been extended to spinels which has made it possible to calculate the various bond parameters for the spinels CuCr₂X₄ and CoCr₂X₄. It has been found that a linear relation exists between the X-ray chemical shift ΔE and C, E_g, and f_i, the ionic energy, total energy and ionici parameters respectively. This fact has been used to determine the various bond parameters in the spinels Cu_0.5Co_0.5Cr_2?xRh_xS₄. It is found that in these spinels a natural balance of ionicity at the A site is maintained, when chromium is gradually replaced by rhodium.     

Calorimetric and x-ray diffraction studies of the (NH4)3WO3F3 and (NH4)3TiOF5 perovskite-like oxyfluorides

The heat capacity and unit cell parameters of the (NH₄)₃WO₃F₃ and (NH₄)₃TiOF₅ perovskite-like oxyfluorides were measured in the temperature interval from 80 to 300 K; the existence of two and one phase transitions in these compounds, respectively, was demonstrated, and their thermodynamic parameters were determined. The effect of a hydrostatic pressure of up to 0.5 GPa on the phase transition temperatures was studied. Triple points and high-pressure phases were found in the T vs. p diagrams. An analysis of entropy changes suggests that all the structural transformations revealed are associated with the ordering of structural blocks. __________ Translated from Fizika Tverdogo Tela, Vol. 46, No. 5, 2004, pp. 888–894. Original Russian Text Copyright ? 2004 by Flerov, Gorev, Fokina, Bovina, Laptash.     

Spectroscopic line parameters of NH3 and PH3 in the far infrared

NH₃ and PH₃ rotation and rotation-inversion line parameters in the far to medium i.r. are calculated for remote sounding purposes of planetary atmospheres; 1607 lines of ¹⁴NH₃, 362 lines of ¹⁵NH₃ and 325 lines of PH₃ are compiled. The absolute intensity formulation has been reviewed in the case of rotation adn rotation-inversion lines of molecules with C_3v symmetry. The justification of the general agreement between the authors, and comparisons with other published expressions are given.     

Anisotropic chemical shifts of 59Co in Co(NH3)6Cl

The chemical shift tensors of ⁵⁹Co in a single crystal of Co(NH₃)₆Cl₃ at the five nonequivalent cobalt sites were measured at room temperature. The principal axes of these tensors almost coincide with the principal directions of the electric field gradient tensors. Assuming that these directions are parallel to the symmetry axes about which the different Co(NH₃)₆³⁺ octahedra reorientate, possible reorientation axes of the octahedra at the five nonequivalent sites are proposed.     

Collision broadening and shifting in the inversion spectrum of NH3

The width and shift parameters for both self-broadened and foreign-gas-broadened lines in the ammonia inversion spectrum have been measured. A dependence on the quantum numbers (J,K) is found for shift parameters, but not for width parameters.     

Chlorine K X-ray absorption-edge structures of CIS-[Pt(NH3)2Cl2], trans-[Pt(NH3)2Cl2], trans-[Pd(NH3)2Cl2] and (NH4)2PdCl4

The K absorption-edge spectra of the ligand chlorine ion in square-planar complex compounds cis- and trans-[Pt(NH₃)₂Cl₂], trans-[Pd(NH₃)₂Cl₂], and (NH₄)₂PdCl₄ are reported and discussed in connection with the chlorine K absorption spectra of K₂PtCl₄ and K₂PdCl₄, reported previously. The observed chemical shift of a white line at the absorption threshold is interpreted in terms of the difference of the ligand-field splitting of electronic states for metal ions. The white line is attributed to the electronic transition from the Cl^? ls level to the lowest unoccupied antibonding molecular orbital (MO), which is specified by a $\text{MO}\text{b}{}_{\mathrm{1g}}\text{(σ}{}^1\text{)}$ in the square-planar complex with D_4h symmetry. The other absorption structures are regarded as continuum “shape resonances” of the outgoing electron trapped by the cage of the surrounding atoms. The effect of geometrical isomerism is found in the chlorine K absorption spectra of cis- and trans-[Pt(NH₃)₂Cl₂].     

Interactions of NH3, coadsorbed with PF3, on Ru(001)

NH₃, coadsorbed with PF₃, on Ru(001) has been studied by temperature programmed desorption (TPD) and high resolution electron energy loss spectroscopy (HREELS). HREELS shows that the P---F stretching frequency decreases by 60–90 cm⁻¹ in the presence of NH₃. This is explained by the enhancement, in the presence of NH₃, of backdonation of electrons from the metal to the antibonding orbital of the PF₃. The PF₃ bending frequency does not change in the presence of NH₃. This indicates that the σ donation of electrons from PF₃ to the metal substrate is not influenced by coadsorbed NH₃. The intensity of the PF₃ vibrational bands, particularly the PF₃ bending mode, decreases drastically in the presence of NH₃. We interpret this in terms of electric field shielding created by the coadsorbed NH₃ and/or the result of direct interactions between NH₃ and PF₃.     

Influence of acceptor and donor adsorbates (CO,K, NH3) on Pt surface core-level shifts

4f core-level shifts have been measured for clean surfaces of Pt(111), Pt(331), and Pt(557). Surface peaks due to terrace sites are shifted toward lower binding energy (0.32 ± 0.05 eV) from the bulk peak, whereas peaks from step atoms are shifted by 0.58 ± 0.05 eV also to lower binding energy. The intensity ratios for the two sites differ considerably between the stepped Pt surfaces. Chemisorption of carbon monoxide on the Pt(331) surface is preferential to step sites, with a Pt 4f binding energy shift of ～ 1.29 eV toward higher binding energy. Chemisorption of potassium and ammonia also produces Pt 4f surface shifts which are at higher binding energy than the bulk peak. These experiments do not support the concept of electron donation by these adsorbates into metal d orbitals. The results are discussed in view of, and supported by, tight-binding LCAOMO calculations of potassium and ammonia interacting with a Pt(111) thin film.     

Magnetic susceptibility studies of (CH2)3(NH3)2FeCl2Br2 and (CH2)6(NH3)2FeCl2Br2

The magnetic susceptibility of the layered compounds (CH₂)₃(NH₃)₂FeCl₂Br₂ and (CH₂)₆(NH₃)₂FeCl₂Br₂ has been measured in the range 80 < T < 300 K. The results follow a Curie-Weiss behavior in the range 120 < T < 300 K but are field dependent for T < 120 K. The results are interpreted in terms of a two-dimensional antiferromagnetic interaction which is canted. A comparison with the corresponding pure chloride compounds is given.