The adsorption of water vapour by lithium fluoride,sodium fluoride and sodium chloride

Water vapour adsorption isotherms have been determined volumetrically on samples of LiF, NaF and NaCl at 278.15, 288.15 and 298.15 K. The surface areas of the samples were determined by krypton adsorption at 77.5 K. Infrared measurements showed the presence of occluded solvents and complete removal of these species was effected under vacuum at the following temperatures; LiF, 823 K; NaF, 723 K; NaCl, 623 K. Except in the case of NaF, for which a BET Type II isotherm was obtained, the krypton isotherms exhibited single sharp steps at the following values of $\text{P}\text{P}{}_0$; LiF, 0.57; NaCl, 0.15. Similarly with water adsorption, the NaF and NaCl isotherms exhibited a single sharp step at the$\text{P}\text{P}{}_0$ values of 0.30 for NaF and 0.35 for NaCl. The isotherm for LiF outgassed at room temperature was of Type II, whilst for LiF outgassed at 673 K it was of Type III. Throughout the water runs no irreversible uptake was observed. The sharp steps in the krypton and water isotherms were attributed to phase transformations in the monolayer. Isosteric heats of adsorption for water vapour were generally invariant with coverage and close to the enthalpy of liquefaction of water. Theoretical adsorption potential energy calculations were carried out for adsorption of a water molecule above four sites on the (100) planes of the three adsorbents. The total adsorption potential was obtained as a sum of the dispersion, electrostatic, induction and repulsion interactions, and for each solid the most favourable adsorption site was above the cation. For adsorption directly above ions, the greatest contribution to the attractive potential was furnished by the electrostatic interaction. Except for the cation values of LiF and NaCl, the theoretical isosteric heats calculated from the potential curves were significantly lower than the experimental isosteric heats. All the samples possessed active sites depending on the adsorbate and outgassing temperature as follows; LiF (Kr, 298 K) 36%, LiF (Kr, 673 K) 15%, NaF (H₂O, 298 K) 18%, NaCl (Kr, 623 K) 20%, NaCl (H₂O, 623 K) 25%.     

Magnetophonon oscilation of thermoelectric power in the conduction band of tellurium

At about 200K where the Hall coefficient of p-Te reverses its sign, magnetophonon oscillation of electron in the conduction band was observed for the first time in H6c and H⊥c. It was attained by measuring the second derivative of the longitudinal magneto-Seebeck coefficient (?²α₆/?H²). It is found to be explained fairly well by a simple parabolic band model even for H6c. Effective mass values of the conduction band at 200K are deduced on an interpretation; $\text{m}{}^1{}_{\mathrm{\perp }}\text{=0.160m}{}_0$ and $\text{m}{}^1{}_6\text{= 0.072m}{}_0$. Rather large contribution of electron in ?²α₆/?H² may be due to the enhanced electron diffusion in a transition region from p-type to intrinsic as reported recently in p-InSb. This interpretation is supported also by the oscillation of longitudinal magnetoresistance (?²?₆/?H²) which was observed for H6c.     

Fourier spectrometry: Rovibrational analysis of an infrared 1Π → 1Σ system of yttrium monoiodide

The infrared spectrum of yttrium monoiodide has been excited in an electrodeless microwave discharge and explored between 2500 and 12 000cm^?1 with a high-resolution Fourier transform spectrometer. A unique system is observed (ν₀₀ = 9905.520 cm^?1), which we attribute to a ${}^1\text{Π}\text{→}{}^1\text{Σ}$ transition and an extensive analysis is made. Rovibrational constants are obtained for both states mainly from a simultaneous multiband fitting. This procedure is applied to the whole set of 2231 observed line wavenumbers in the 1-0, 0-0, and 0–1 bands, yielding a final weighted standard deviation of 0.0038 cm^?1. Furthermore, a partial analysis of the 2-0 and 3-1 bands is performed. The following equilibrium constants are derived (cm^?1):

$\text{ω′}{}_{\mathrm{e}}\text{=192.210 ω′}{}_{\mathrm{e}}\text{x′}{}_{\mathrm{e}}\text{=0.463}$

$\text{B′}{}_{\mathrm{e}}\text{=0.0399133 α′}{}_{\mathrm{e}}\text{=0.0001150}$

$\text{ω″}{}_{\mathrm{e}}\text{=215.815 ω″}{}_{\mathrm{e}}\text{x″}{}_{\mathrm{e}}\text{=0.514}$

$\text{B″}{}_{\mathrm{e}}\text{=0.0422163 α″}{}_{\mathrm{e}}\text{=0.0001125}$

High-order constants D_v and H_v are also calculated for the various vibrational levels (v′ = 0, 1, 2, 3; v″ = 0, 1).     

Etude des proprietes thermodynamiques d'un groupement tetranucleaire: Application au compose Na3RuO4

The exact eigenvalues spectrum of the spin hamiltonian $\text{H}\text{= ?2}\text{∑}\text{(i, j)}\text{J}{}_{\mathrm{ij}}\text{S}\text{?}{}_{\mathrm{i}}\text{S}\text{?}{}_{\mathrm{j}}$ have been calculated for a tetranuclear cluster formed by four spins 3/2 at the vertices of a lozenge. Two isotrope exchange interactions J₁ and J₂ are able to explain the thermodynamic properties (magnetic susceptibility, entropy, specific heat). A ground state transition from singlet to triplet state occurs when the $\text{J}{}_2\text{J}{}_1$ ratio reaches the value $\text{4}\text{3}$. The magnetic susceptibility data of Na₃RuO₄ fit well with the theoretical values proposed for $\text{J}{}_1\text{K}\text{= (?19,5 K)}$ and J₂/k (?22,5 K).     

Spin wave spectrum of Ca2MnO4 at 4.2K

The spin-wave spectrum of Ca₂MnO₄ has been measured at 4.2K. It can be fully built from two exchange integrals in the (001) plane $\text{J}{}_{\mathrm{<mtext>1</mtext>}}\text{=}\text{5.9}$ meV and $\text{J}{}_{\mathrm{<mtext>2=1.7\; meV</mtext>}}$, and in out-of plane exchange integral $\text{J}\text{′}{}_{\mathrm{<mtext>1</mtext>}}\text{=}\text{0.6}\text{meV}$. This latter explains quite well the splitting of the magnon dispersion curve.     

The dipole moment of thioformaldehyde in its singlet and triplet π1 − n excited states

Laser-induced fluorescence excitation has been used to measure Stark splittings of selected lines in the $\text{A}\text{?}{}^1\text{A}{}_2\text{-}\text{X}\text{?}{}^1\text{A}{}_1$ and $\text{a}\text{?}{}^3\text{A}{}_2\text{-}\text{X}\text{?}{}^1\text{A}{}_2$ band systems of H₂CS in electric fields up to 13 kV/cm. The derived excited state a-axis dipole moments are 0.820 ± 0.007 D for the 4¹ level of the ¹A₂ state; 0.838 ± 0.008 D for the zeroth vibrational level of ¹A₂; and 0.534 ± 0.015 D for the zeroth vibrational level of the ³A₂ state. These results are compared with the corresponding values of H₂CO, and interpreted in terms of the changing localization of the π and $\text{π}{}^1$ orbitals accompanying electronic excitation.     

The surface structure of V(100)

The structure of the clean V(100)?(1×1) surface is determined, based on an r-factor comparison of experimental LEED intensity-energy spectra with the results of multiple-scattering model calculations. Minimization of the r-factor with respect to the calculational variables leads to optimum values of the first and second interlayer spacings of $\text{d}{}_1\text{=1.41 ± 0.01}\text{A}\text{?}$ and $\text{d}{}_2\text{=1.53 ±0.01}\text{A}\text{?}$, corresponding respectively to a contraction of 7% and an expansion of 1% with respect to the bulk value of $\text{d}{}_{\mathrm{<mtext>B</mtext>}}\text{=1.5141}\text{A}\text{?}$. Preliminary studies of the adsorption of O₂ and CO confirm that the V(100)?(5×1) structure observed during the process of cleaning the crystal is not characteristic of the clean surface, as suggested recently by Davies and Lambert (Surface Science 107 (1981) 391), but rather is associated with the presence of a significant concentration of oxygen in the surface region.     

Effective Hamiltonian for polyatomic linear molecules

The leading terms of an effective Hamiltonian for a linear molecule in a given vibrational state are presented up to κ¹⁰T_v order of magnitude, whereby higher-order l-dependent terms such as $\text{H}\text{?}{}_{12.0}$, $\text{H}\text{?}{}_{8.0}$, and $\text{H}\text{?}{}_{8.2}$ have been neglected because in spectroscopic application they are of minor importance. This Hamiltonian therefore includes all those l-type interactions which could contribute to the fitting procedure, within a vibrational state where one or more bending vibrations are excited.     

Thermochemistry of azide salts and the azide ion using direct minimisation equations to obtain the lattice energy of the univalent azide salts

The opportunity to test a new equation for the computation of the lattice energy and at the same time examine a disparity in the literature data for the enthalpy of formation of the azide ion, $\text{ΔH}{}^{\mathrm{\theta }}{}_{\mathrm{?}}\text{(}\text{N}{}_3{}^{\mathrm{?}}\text{) (}\text{g}\text{)}$ was the motivation for this study. The results confirm our earlier calculation and show the new equation to be reliable. Thermodynamic data produced in the study take values: $\text{ΔH}{}^{\mathrm{\theta }}{}_{\mathrm{?}}\text{(}\text{N}{}_3{}^{\mathrm{?}}\text{)(}\text{g}\text{) = 144}\text{kJ mor}{}^{\mathrm{?1}}$ΔH^θ_hyd(N₃^?) = ?315 KJ mol^?1 or ΔH^θ_hyd(N₃^?) = ?295 KJ mol^?1U_POT(NaN₃) = 732 kJ mol^?1U_POT(KN₃) = 659 kJ mol^?1U_POT(RbN₃) = 637 kJ mol^?1U_POT(CsN₃) = 612 kJ mol^?1U_POT(TIN₃) = 689 kJ mol^?1. The lattice energies of azides whose enthalpies of formation are documented have been calculated as well as the enthalpy of formation of the azide radical.     

Concepts of convergence for a quantum law of large numbers

We introduce the notion of uniform convergence of an operator sequence relative to a state operator, and we compare it with the notion of almost everywhere convergence, introduced by Gudder. We show that a sequence (M_n) of mean-value operators

$\text{M}{}_{\mathrm{n}}\text{=}\text{1}\text{n}\text{∑n}\text{i=1}\text{1?…?A}{}_{\mathrm{i}}\text{?1?…,}$

defined on the infinite tensor product $\text{?}\text{i}\text{H}{}_{\mathrm{i}}$, converges relative uniformly to $\text{x}\text{1}$ if and only if it converges almost everywhere to $\text{x}\text{1}$.     

Reorientational motion of the OH− ion in cubic sodium hydroxide

The rotational motion of the OH^? ion was studied in cubic NaOH at 575 K with quasielastic incoherent neutron scattering. The data are compared to two simple models yielding values for the radius of rotation R, the translational mean square displacement 〈u²〉_H, the rotational jump rate τ^?1 and the rotational diffusion coefficient D_R. The following parameter values are obtained: (a) rotational jump model: $\text{R = 0.95}\text{A}\text{?}$, $\text{〈u}{}^2\text{〉}{}_{\mathrm{H}}\text{= 0.052}\text{A}\text{?}{}^2\text{, τ}{}^{\mathrm{?1}}\text{= 2}\text{meV}$, (b) rotational diffusion model: $\text{R = 0.99}\text{A}\text{?}\text{, 〈u}{}^2\text{〉}{}_{\mathrm{H}}\text{= 0.046}\text{A}\text{?}{}^2\text{, D}{}_{\mathrm{R}}\text{= 0.72}\text{meV}$.     

Low temperature specific heats of nearly one-dimensional antiferromagnet: CuCl2·2NC5H5

Transition temperature to LRO state was found at T_N=1.14K for nearly one-dimensional antiferromagnet CuCl₂ · 2NC₅H₅. Intra- and inter-chain exchange constants J and J′ were estimated, $\text{kT}{}_{\mathrm{<mtext>N</mtext>}}\text{J}\text{=0.082}$ and $\text{J′}\text{J}\text{=3×10}{}^{\mathrm{?3}}$, respectively. Comparison with those of TMMC implies highly one-dimensional character.     

Vibrational spectra and force constants of symmetric tops: High resolution spectra of monoisotopic H3SiCl in the 2200-cm−1 region and rovibrational analysis of the ν1 and ν4 fundamentals

The gas phase infrared spectra of monoisotopic H₃Si³⁵Cl and H₃Si³⁷Cl have been studied in the $\text{ν}{}_1\text{ν}{}_4$ region near 2200 cm^?1 with a resolution of 0.012 and 0.04 cm^?1, respectively, and rotational fine structure for ΔJ = ±1 branches has been resolved. In addition, some information on ν₃ + ν₄ of H₃Si³⁵Cl near 2750 cm^?1 has been obtained. ν₁ and ν₄ are weakly coupled by Coriolis x, y resonance, $\text{B}\text{Ω}{}_{14}\text{ζ}{}_{14}\text{～ 2 × 10}{}^{\mathrm{?3}}\text{cm}{}^{\mathrm{?1}}$, only the upper states K′ = 2, l = 0 and K′ = 1, l = ?1 being substantially affected. Local perturbation due to rotational l(±1, ±1)-type resonance with ν₃ + ν₅⁺¹ + ν₆⁺¹ and ν₃ + ν₅⁺¹ + ν₆^?1 is revealed in the ΔK = +1 and ?1 branches, respectively. From a fit of the experimental line positions, standard deviations of 1.4 and 3.8 × 10^?3 cm^?1, respectively, to a model with five interacting levels conventional excited state parameters and interaction constants have been obtained. In $\text{H}{}_3\text{Si}{}^{35}\text{Cl}\text{H}{}_3\text{Si}{}^{37}\text{Cl}$ the fundamentals are ν₁, $\text{2201.94380(15)}\text{2201.9345(7)}$ and ν₄, $\text{2209.63862(8)}\text{2209.6254(2)}\text{cm}{}^{\mathrm{?1}}$, respectively. Q branches of the “hot” band (ν₃ + ν₄) ? ν₃ and of ν₄ of the ²⁹Si and ³⁰Si species have been detected.     

The nuclear quadrupole interaction in Pr3+:LaF3 — An optical-RF double resonance measurement of the ground electronic state

The nuclear quadrupole hyperfine splittings of Pr³⁺ in LaF₃ have been measured for the ground electronic state using a RF optical resonance technique. A hamiltonian $\text{H}\text{= P[(I}{}^2{}_{\mathrm{z}}\text{?}\text{1}\text{3}\text{I(I+1) + (η/6)(I}{}^2{}_{\mathrm{+}}\text{?I}$²_-)] was fitted to the data with zP=4.185 ± 0.003 MHzandη = 0.105 ± 0.010. Linewidths of 180 kHz were observed.     

Theory of negative magnetoresistance in three-dimensional systems

Theory of negative magnetoresistance in two-dimensional systems due to delocalization of electrons by magnetic field by Hikami, Larkin, and Nagoaka is extended to the case of three-dimension. The increase in conductivity by magnetic field is independent of the direction of the current relative to that of the magnetic field, and is proportional to $\text{H}{}^2\text{τ}{}_{\mathrm{?}}{}^{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$, τ_? being energy relaxation time of electrons, when the magnetic field H is small. If τ_? is large enough at low temperature and H is not too small, it is independent of the parameter characterizing the system, and is of the form $\text{0.918?H mho cm}{}^{\mathrm{?1}}$ (H in kOe).     

Infrared spectrum of acetonitrile: Analysis of Coriolis resonance

The Coriolis resonance between ν₄ and ν₇ in CH₃CN and between ν₁ and ν₅, ν₃ and ν₆, and ν₄ and ν₇ in CD₃CN has been analyzed, applying the technique developed by DiLauro and Mills, to obtain the signs of [$\text{ζ}{}_{\mathrm{r,sa}}{}^{\mathrm{y}}\text{(}\text{?p}\text{?Q}{}_{\mathrm{r}}\text{)(}\text{?p}\text{?Q}{}_{\mathrm{sa}}\text{)}$] and the ratio of $\text{?μ}\text{?Q}{}_{\mathrm{r}}$ to $\text{?μ}\text{?Q}{}_{\mathrm{s}}$ for the interacting pairs in CD₃CN. For (ν₄, ν₇) in both CH₃CN and CD₃CN, the sign of [$\text{ζ}{}_{\mathrm{r,sa}}{}^{\mathrm{y}}\text{(}\text{?p}\text{?Q}{}_{\mathrm{r}}\text{)(}\text{?p}\text{?Q}{}_{\mathrm{sa}}\text{)}$] is found to be negative as it is also for (ν₁, ν₅) in CD₃CN. For (ν₃, ν₆) the sign of this interaction term is found to be positive. For a given definition of normal coordinates the signs of these interaction terms give the relative signs of $\text{?p}\text{?Q}{}_{\mathrm{r}}$ and $\text{?p}\text{?Q}{}_{\mathrm{sa}}$; our study also gives approximate values for the corresponding ratio [$\text{(}\text{?p}\text{?Q}{}_{\mathrm{r}}\text{)}\text{(}\text{?p}\text{?Q}{}_{\mathrm{sa}}\text{)}$]     

Microwave spectrum and structure of cyanamide: Semirigid bender treatment

An extensive study of the microwave spectrum of cyanamide has been undertaken, the analysis being based in part on semirigidbender calculations by the methods of Bunker and Szalay. Inversion lines of NH₂CN, $\text{K}{}_{\mathrm{?1}}\text{= 2}{}^{\mathrm{a}}\text{Q}$ branches and a number of vibrational satellites of the J = 2?1 transition were observed. A two-vibrational-state Hamiltonian was used to fit simultaneously the 0⁺ and 0^? microwave data and yielded rotational constants X, Y, Z, D_J, D_JK, d₁, H_JK as well as the inversion splitting and the μ_yz-connecting matrix element. Vibrational satellite data of seven isotopic species and infrared frequencies of NH₂CN were included in the semirigid bender calculations: The NCN spine is nonlinear by ca. 5° in the equilibrium structure of the molecule. Also, $\text{r}{}_{\mathrm{<mtext>NH</mtext>}}\text{A}\text{?}\text{= 0.9994 + 0.0144?}{}^2$; <HNH/2 = 60.39° ? 0.1134?²; $\text{r}{}_{\mathrm{<mtext>NC</mtext>}}\text{A}\text{?}\text{= 1.3301 + 0.0327?}{}^2$ (? is the inversion angle in rad); $\text{r}{}_{\mathrm{<mtext>CN</mtext>}}\text{= 1.1645}\text{A}\text{?}$ fixed. The inclusion of the NC bond flexing was necessary in order to reproduce the observed vibrational satellite patterns of NH₂CN, NHDCN, and ND₂CN. The barrier to inversion of the amino group is 510 ± 6 cm^?1 with minima at ±45.0 ±0.2°. The inversion dipole moment is 0.91 ± 0.02 Debye.     

A theoretical model for the interacting upper states of the ν1, ν3, 2ν2, ν2 + ν4, and 2ν4 bands in methane

The effective vibration-rotation Hamiltonians complete to fourth order in the Amat-Nielsen scheme for the upper states of the ν₁, ν₃, 2ν₂, ν₂ + ν₄, and 2ν₄ bands in methane are reviewed, and the major vibration-rotation interactions (H₃₀, $\text{H}\text{?}{}_{40}$, $\text{H}\text{?}{}_{21}$, $\text{H}{}_{31}$, $\text{H}\text{?}{}_{22}$) connecting the different vibrational states are discussed. Explicit matrix elements in a basis of harmonic oscillator-symmetric rotor basis functions are given for the purely vibrational terms and for the vibration-rotation interactions. Expressions for spectral intensities of infrared and Raman spectra are presented, and the selection rules and transition moment matrix elements are stated. A computer program is described which, incorporating all these features, can be used for prediction of infrared and Raman spectra and for determination of molecular constants from observed spectra by a least-squares routine. As an example the program is applied to the 2ν₄ isotropic Raman spectrum of ¹²CH₄, leading to a very good agreement between the experimental and calculated spectra.     

Temperature dependence of the ESR spectra of Mn2+ in iron pyrite (FeS2)

The first observation of the ESR spectra of Mn²⁺, entering substitutionally for Fe²⁺ in the Van Vleck paramagnet FeS₂ (polycrystals), is reported. The data from 5 to 295 K fits the spin-Hamiltonian $\text{h}{}_{\mathrm{s}}\text{= gβ}\text{H}\text{·}\text{S}$ + $\text{[S}{}^{\mathrm{<mtext>2</mtext>}}{}_{\mathrm{z}}\text{?}\text{1}\text{3}\text{S(S + 1)] + A}\text{S}\text{·}\text{I}$, with g = 2.000 ± 0.001, A/β = ?95.0 ± 0.5 Oe and D/β varying from 50 Oe (5K) to 59 Oe (295 K). The temperature dependence of D can be described in terms of a single phonon-mode with frequency ? 145 cm^?1.