Rotation-vibration energy levels of H2O and C3 calculated using the nonrigid bender Hamiltonian

We have written a new computer program for diagonalizing the nonrigid bender Hamiltonian, and have based the program entirely on the theory as reviewed by P. Jensen [Comp. Phys. Rep. 1, 1–56 (1983)] and P. Jensen and P. R. Bunker [J. Mol. Spectrosc. 118, 18–39 (1986)]. Using this program we can calculate the rotation-vibration energy levels of a triatomic molecule from the potential energy function. The program is an improvement over an earlier version, particularly in the systematic treatment of all singular terms, and in the allowance made for the dependence of all perturbation energy denominators on the bending quantum number v₂ and rotation quantum number K. The new program can be used for symmetric and unsymmetric triatomic molecules. In the present paper we test the program by applying it to the calculation of the rotation-vibration energy levels of C₃ from an ab initio potential surface, and of H₂O from ab initio and experimental potential surfaces.     

Global variational calculations of high-resolution rovibrational spectra: isotopic effects,intensity anomalies and experimental confirmations for H2S,HDS, D2S molecules

Variational calculations of high-resolution infrared molecular spectra for isotopically substituted triatomic molecules from potential and dipole moment functions are discussed. A study of intensity anomalies and of their isotopical behavior especially for symmetry-breaking substitutions represents a particularly interesting subject. Extreme manifestations of intensity anomalies present in spectra of the hydrogen sulfide molecule are considered. A first qualitative experimental confirmation of reported theoretical results for deuterium containing species is discussed. To cite this article: Vl.G. Tyuterev et al., C. R. Physique 5 (2004).     

On some low-temperature properties of (La, Ce)B6 alloys

Some recent experimental data on the magnetic susceptibility and the low-temperature magnetization of the (La, Ce)B₆ system are discussed in the light of the theoretical results. A value of the s-f exchange constant J is estimated which is also consistent with the results obtained from both the Kondo effect and the RKKY interaction.     

τ Dependence of the vibrational zeropoint energy in the partially deuterated methyl alcohols,revisited

The contributions of the zeropoint energy from the 3N ? 7 other vibrations to the effective potential energy for internal rotation have been calculated for eight isotopic species of methyl alcohol. The basis of the calculation is the set of force constants determined by A. Serrallach, R. Meyer, and Hs. H. Günthard [J. Mol. Spectrosc.52, 94–129 (1974)] from infrared analyses. The results calculated for CH₂DOH are V₁ = 11.93 cm^?1 and V₂ = 0.17 cm^?1 with ΔV₃ < 0.05 cm^?1. These values agree favorably with the experimental results as previously determined from analysis of the microwave torsional-rotational spectra of CH₂DOH.     

Internal hydrogen bond,torsional motion,and molecular properties of 2-methoxyethylamine by microwave spectroscopy: Methyl barrier to internal rotation for 2-methoxyethanol

The microwave spectra of four substituted isotopic species of 2-methoxyethylamine (NH₂, NHD, NDH, ND₂) have been assigned. The molecule is found to exist in a gauche form with an intramolecular hydrogen bond of the NH?O type. The four possible sets of the amino hydrogen r_s corrdinates give different H?H distances, probably because the -NH₂ group is involved in large amplitude vibrations and because of changes in the heavy atom positions arising from the deuteration of the hydrogen bond. For the most abundant species many vibrational states have been analyzed and assigned to the two possible CO torsions in the molecule. A value V₃ = 3150 ± 50 cal/mol was found for the methyl torsional barrier and V₁ = 9 ± 3 kcal/mol for the other CO torsional barrier. A third set of observed vibrational satellites is probably assignable to the CC torsion. The determination of the dipole moment and of the quadrupole coupling constants gave values which were not in good agreement with those predicted from nonhydrogen bonded molecules. In addition a value V₃ = 3100 ± 100 cal/mol was calculated for the CH₃ torsional barrier in the related 2-methoxyethanol, using previous experimental data (Canad. J. Chem.50, 1149–1156 (1972)).     

Multiparameter model functions in problems of approximating ab initio potentials and spectroscopic data of diatomic molecules

A new multiparameter function of the generalized Morse long-range potential is presented. All earlier similar constructions turn out to be particular cases of this new function. The operation technique for this function is described. Using realistic test examples (ab initio potentials of the K₂ molecule and “experimental” spectroscopic data calculated by them), the possibilities of this function are compared with those of the most developed form of the piecewise continuous model potential in problems of direct optimization modeling of potential functions and in problems of optimization modeling of experimental data aiming at determining potentials. A conclusion is drawn that, although the two classes of functions lead, in general, to comparable results in quality, the piecewise continuous approximant permits one to achieve a better reproduction of the modeled data in some cases. Using the available collection of experimental data, parameters of the piecewise continuous approximant were determined for the potentials of the 1 _g (3³Π _g ) and a ³Σ _u ⁺ states of the Cs₂ molecule, for which we previously constructed potentials in the form of a generalized Morse function (J. Chem. Phys. 135, 024303 (2011)).     

Triboelectric charging of insulators – Mass transfer versus electrons/ions

In a recent publication on the mechanisms of triboelectric charging of insulators we interpreted our experimental results in terms of electron and ion transfer. We now report that these results can equally well be interpreted by the mass transfer mechanism. A process is proposed to distinguish between these. This would provide information relating to the idea that classification of triboelectric mechanisms of insulators may result from considering the amount of applied forces and frictional energy involved in the process, thus distinguishing between the mechanisms of non-frictional contact and pressing or rubbing contacts.     

Ab initio SCF-Cl studies on the large amplitude bending motion of the water molecule: Rigid,semirigid, and nonrigid bender models for the Hamiltonian

Self-Consistent Field (SCF) and Configuration Interaction (CI) studies are performed on the bending mode of the water molecule using a double zeta plus polarization basis set. The ab initio points are fitted to a three-parameter double minimum potential consisting of a quadratic plus Lorentzian terms. The vibration-rotation energies are then evaluated using the large amplitude Hamiltonian developed by P. R. Bunker and co-workers at various levels of approximations. It is found that the calculated frequencies improve significantly as one proceeds from approximate H_b⁰⁰(ρ) to rigid bender H_b⁰(ρ) [P. R. Bunker and J. M. R. Stone, J. Mol. Spectrosc.41, 310–332 (1972)] to semirigid bender H_b⁰(r, ρ) [P. R. Bunker and P. M. Landsberg, J. Mol. Spectrosc.67, 374–385 (1977)] Hamiltonian. With H_b⁰(r, ρ), the ab initio calculated bending frequency ν₂ differs from the observed value (1595 cm^?1) by 30 cm^?1 and the barrier height is 12 229 cm^?1. It is also shown that ν₂ and its first four overtones are better calculated by 45–98 cm^?1 when the ab initio potential is used directly instead of the three-parameter analytic potential fitted to ab initio data. Finally, rotation bending energy levels are calculated for v₂ ≤ 3 and J ≤ 10 on the basis of a nonrigid bender Hamiltonian of A. R. Hoy and P. R. Bunker [J. Mol. Spectrosc.74, 1–8 (1979)], using the ab initio quadratic force field of P. Hennig, W. P. Kraemer, G. H. F. Diercksen, and G. Strey, [Theor. Chim. Acta47, 233–248 (1978)]. These results show that the accuracy of calculated force constants and frequencies is critically dependent not only on the size of the basis set but also on the number and spacing of the ab initio points used to derive the force field.     

Synthesis,structure and luminescence properties of a series of dinuclear LnIII complexes (Ln=Gd,Tb, Dy,Ho, Er)

The reactions of lanthanide nitrates with a Schiff-base ligand HL (2-[(2-hydroxypropylimino)methyl] phenol) have produced five new complexes with formula as [Ln₂(L)₃(NO₃)₃]CH₃OH(Ln=Gd 1, Tb 2, Dy 3, Ho 4, Er 5). These new complexes are characterized by elemental analysis, IR and X-ray diffraction, as well as fluorescence spectra. Single-crystal X-ray diffraction analysis reveals that all the complexes crystallize in the trigonal system, space group R-3. Fluorescence spectroscopy of Tb(III) and Dy(III) complexes display strong characteristic metal-centered fluorescence in solid state, which demonstrates that luminescence is sensitized by the effective energy-transfer from ligand to the metals. The fluorescence lifetimes of complex 2 and 3 are also determined.     

An improved acoustic method for the determination of the Boltzmann constant at LNE-INM/CNAM

There is currently great interest in the international metrology community for new accurate determinations of the Boltzmann constant k, with a view to a new definition of the unit of thermodynamic temperature, the kelvin. Indeed, k is related to the quantum of energy kT, where T is the thermodynamic temperature.The value of the Boltzmann constant can be obtained from measurements of the velocity of the sound in a noble gas. In the method described here, the experiment is performed in a closed spherical cavity. To obtain an accurate value for k, all the parameters of the experiment (gas purity, static pressure, temperature of the device, exact shape of the cavity, etc.) have to be carefully controlled. As correction terms have to be applied to the acoustic signals, the validity of the theoretical models from which they are derived is crucial.The new determination carried out at the LNE-INM/CNAM is based on the same principles as in the acoustic experiment of Moldover et al. at NIST in 1988, which led to the most accurate determination of the Boltzmann constant up to now. However, several fundamental modifications and improvements have been made in this new experiment to measure and control the parameters that set the measured value of k. To cite this article: L. Pitre et al., C. R. Physique 10 (2009).     

Quarks and gluons: tests of QCD in e+e− annihilations

This article gives an overview of the main experimental tests of perturbative QCD performed at LEP. It covers the following topics: determination of α_s from event shapes, tests of flavour independence of α_s, studies of heavy quark mass effects, differences between quark and gluon jet fragmentation and study of the triple gluon vertex. To cite this article: D. Duchesneau et al., C. R. Physique 3 (2002) 1211–1222.     

Experimental determination of the critical exponent η for nickel

The first unambiguous experimental determination of the critical exponent η, describing the critical point line shape of the spin correlation function, is presented for a three dimensional magnetic system. As a consequence of a finite value of η the critical scattering displays a maximum at T_max(q) above the Curie temperature T_c. The shift of the maximum with increasing scattering vector q was observed by a neutron small-angle experiment, yielding η=0.041±0.009 for a nickel single-crystal.     

Reference deconvolution. Elimination of distortions arising from reference line truncation

Reference deconvolution (G. A. Morris; J. Magn. Reson. 80, 547 (1988)) or reference lineshape adjustment (J. M. Wouters and G. A. Petersson, J. Magn. Reson. 28,81 (1977); J. M. Wouters, G. A. Petersson, W. C. Agosta, F. H. Field, W. A. Gibbons, H. Wyssbrod, and D. Cowburn, J. Magn. Reson. 28, 93 (1977)) relies on extracting the signal of a known reference material from an experimental spectrum and using a comparison between the experimental reference signal and that predicted by theory to correct instrumental contributions to the full experimental spectrum. Truncation of the reference line can produce unwanted artifacts and distortions in the final spectrum. The source of these anomalies usually lies in the dispersion-mode rather than in the absorption-mode data, as discontinuities are formed when the dispersion “wings” are truncated. These discontinuities can be reduced by a numerical extrapolation covering the lost region; this is sufficient to provide adequate results in most cases, but fails where spectra have baseline errors. A method of recreating the full dispersion signal directly from the corresponding adsorption data, based on the Hilbert transform relationship between the real and imaginary parts of a Fourier transform, is demonstrated here. This method results in the removal of truncation distortions from the deconvoluted spectrum, thus extending the range of application of the reference deconvolution technique.     

A Three-Component Model for Magnetization Transfer. Solution by Projection-Operator Technique,and Application to Cartilage

A projection-operator technique is applied to a general three-component model for magnetization transfer, extending our previous two-component model [R. S. Adler and H. N. Yeung,J. Magn. Reson. A104,321 (1993), and H. N. Yeung, R. S. Adler, and S. D. Swanson,J. Magn. Reson. A106,37 (1994)]. The PO technique provides an elegant means of deriving a simple, effective rate equation in which there is natural separation of relaxation and source terms and allows incorporation of Redfield–Provotorov theory without any additional assumptions or restrictive conditions. The PO technique is extended to incorporate more general, multicomponent models. The three-component model is used to fit experimental data from samples of human hyaline cartilage and fibrocartilage. The fits of the three-component model are compared to the fits of the two-component model.     

Coulomb oscillations of the ballistic conductance in a quasi-one-dimensional quantum dot

It is demonstrated that localized states of an open quasi-one-dimensional quantum dot can be charged by the Coulomb blockade mechanism. A new effect—Coulomb oscillations of the ballistic conductance—is observed because of the high sensitivity of the ballistic current to single-electron variations of the self-consistent potential of the dot. The model proposed explains experimental results [C.-T. Liang, M.Y. Simmons, C. G. Smith, et al., Phys. Rev. Lett. 81, 3507 (1998)].     

Spin and orbital angular momenta defined for electromagnetic fields in planar anisotropic media

The spin and orbital angular momenta (S and L) of the radiation fields were defined newly to satisfy the duality transformation and to hold for planar anisotropic media, by introducing an entirely new vector potential. Some features of them are discussed in connection with the anisotropy in the permittivity and permeability of a medium.     

Bulk magnetization study of a DyNi5 single crystal

Magnetization and susceptibility measurements were performed on a single crystal of DyNi₅ along the three main symmetry axes of the ortho-hexagonal cell. Below its ordering temperature (T_c = 11.6 K), b and c are respectively the easy and hard magnetization axes. The strong anisotropy originates from the crystalline electric field acting on the 4f electrons of the Dy³⁺ ions. A small magnetization is induced on nickel atoms by the applied field and the exchange interactions with the dysprosium atoms. The crystal field parameters, the molecular field coefficients and the susceptibility of nickel atoms are determined from the experimental data.     

Sufficient conditions for the existence of bound states in a potential without spherical symmetry

We give in this paper several suffieient conditions for the existence of negative energy bound states in a purely attractive potential without spherical symmetry. These conditions generalize the condition obtained recently by K. Chadan and A. Martin (C. R. Acad. Sci. Paris290 (1980), 151), and can ensure the existence of n bound states. For the spherically symmetric case, one gets simple formulae which are also new.     

Experimental determination of the scattering length for positron scattering from krypton

We report the first experimentally supported determination of the scattering length for positron scattering from krypton. Our result of  ?10.3 ± 1.5 a.u. compares favourably with that from a convergent close coupling calculation performed as a part of this investigation (?9.5 a.u.), and also with an earlier many body theory calculation of  ?10.1 a.u. from Gribakin and Ludlow [Phys. Rev. A 70, 032720 (2004)] and a polarized-orbital result of  ?10.4 a.u. from McEachran et al. [J. Phys. B 13, 1281 (1980)]. The present experimental scattering length supports the existence of a low-lying positron-krypton virtual state (Surko et al. [J. Phys. B 38, R57 (2005)]) at an energy ε = 0.13 eV.