Effect of dipole-dipole intermolecular forces in the vibration spectra of organic compounds

The potential energy of a polar liquid is derived from the electrostatic interaction of point dipoles, taking into account the formation of local groups with short-range order with minimum energy. The methods of classical mechanics are used to estimate the effects of interaction on the normal vibration frequencies. It is shown that interaction increases the frequencies of low-frequency dipole-rotation vibrations; frequencies of other types may increase or decrease.I am indebted to Professor N. A. Prilezhaeva for discussing these results.     

Development of dipole-dipole intermolecular forces in the vibration spectra of organic compounds

Possible line broadening of the vibrational spectra of organic liquids as a result of intermolecular vibrational reactions has been theoretically assessed. It has been shown that the frequency scattering connected with fluctuations in the energy of local electrostatic forces can explain the width observed in some cases. It has been found possible to link line broadening with the temperature behavior of the frequencies.The author would like to express his sincere thanks to N. A. Prilezhaev for his interest in this work and for valuable discussions of it.     

Appearance of intermolecular interaction in the vibrational spectra of polyatomic XY3 molecules

We present the Raman spectra of liquid and solid PBr₃, AsCl₃, AsBr₃, and BiCl₃ between 77 and 500°K. We conjecture that ethane-like dimers of these phosphorus and arsenic trihalides exist between some temperature and the melting point. On the basis of our experimental results we analyze the change in the intramolecular force field of these molecules induced by the phase transitions and temperature, whence we calculate the frequency of vibration of the molecules relative to each other in the dimers: 2PBr₃, 2AsCl₃, 2AsBr₃. The same approach also gives the frequencies of the librational and translational modes of bismuth trichloride at 77°K.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 42–49, April, 1977.     

Manifestation of dipole-dipole intermolecular forces in VI-brational spectra of organic compounds

The temperature dependence of line width in the Raman spectra of acetonitrile and benzonitrile in the liquid state was investigated experimentally by photographic and photoelectric methods. By excluding the effect of dipole-dipole broadening from the observed line width, the temperature dependence of the component width due to rotational Brownian motion of the molecules in the liquid was revealed. It was found that the parameters of the rotational Brownian motion undergo sharp changes near the crystallization points of the liquids. To explain this effect it is suggested that molecular association occurs in the liquid at low temperatures under the influence of dipole-dipole forces. By simple calculations, an assignment is made of the frequencies of benzonitrile in the low-frequency region, and the forms of the molecular vibrations are established.     

Effect of dipole-dipole intermolecular forces on the vibrational spectra of organic compounds

Raman line widths were measured for monosubstituted benzene, -picolene and -chloronaphthalene in the liquid phase at various temperatures. Factors affecting the linewidth are analyzed theoretically.The authors are greatly indebted to N. A. Prilezhaeva for her constant attention and valuable advice.     

Anisotropic intermolecular forces

Anisotropic intermolecular potentials for Ar · HF, Kr · HF and Xe · HF are obtained by least squares fitting to molecular beam spectra of van der Waals complexes. The absolute minimum is at the linear rare gas-HF geometry for all the systems considered. The potentials are reliable around the absolute minimum, but the existing data are not sensitive to the behaviour elsewhere. In particular, the absolute well depths and the behaviour around the linear rare gas-FH geometries are not well determined and depend upon the model chosen. Experiments which would provide further information on the potentials for HF systems are suggested.

The potentials for the rare gas-HF systems are considerably more anisotropic than for the corresponding rare gas-HCl systems. The contributions of induction and dispersion forces to the potential anisotropy are discussed and both are found to be significant. It seems likely that the attractive forces can be adequately described in terms of induction and dispersion forces alone, without the need to invoke incipient chemical bonding.     

Normal forces of magnetorheological fluids under oscillatory shear

The normal forces of magnetorheological fluids under oscillatory shear are investigated by a commercial magneto-rheometer with plate-plate geometry. At the constant strain amplitude and frequency, the normal forces almost keep a steady value with the testing time if the strain amplitude is smaller than the critical value. When a larger strain is applied, they will fluctuate periodically. Under the strain sweep mode, the relationships between normal forces and strain amplitude can be divided into three regions: linear viscoelastic region, nonlinear viscoelastic region and the viscoplastic region. Under the frequency sweep method, it is found that the angular frequency show little influence on the normal forces. At last, the normal forces increase with increasing of the temperature under a low magnetic field, while they decrease under a high magnetic field.     

Manifestation of dipo le-di pole intermolecular forces in organic compounds

Raman spectra were obtained for -, -, and -picolines in the gaseous state and in the liquid at various temperatures. Most of the observed frequencies were assigned by comparison with the spectra of pyridine and toluene. A phase shift was observed in the frequencies on passing from gas to liquid; it was interpreted in terms of local dipole-dipole interactions, and a correlation was established with the dipole moment of the molecule. The widths of a series of lines in the spectra of the picolines in the liquid state were measured. Analysis of the results revealed a relative contribution from Brownian rotational movement of the molecules and fluctuations of the dipole-dipole forces.Translated from Izvestiya VUZ. Fizika, Vol. 11, No. 8, pp. 87–93, August, 1968.The authors thank M. F. Vuks for kindly providing the compounds.     

The statistical correlation of intermolecular coriolis and centrifugal forces

Correlation functions are computed in the laboratory frame for the molecular coriolis and centrifugal forces with respect to a frame of reference static in the laboratory. The molecular Coriolis and centrifugal forces in this laboratory frame result from a combination of the molecule's rotational and translational motion, and correlate statistically these two types of motion. They are not usually considered in the theory of decoupled rotational or translational diffusion. Correlation functions are computed for the enantiomers and racemic mixture of liquid bromochlorofluoromethane, and for dichloromethane liquid subjected to a strong, uniaxial, electric field of force in the z axis of the laboratory frame.     

Vibrational-spectroscopy study of intermolecular dynamics of condensed matter IV. Temperature dependence of the low-frequency Raman scattering spectra of certain organic compounds

An experimental study was made of the Raman scattering spectra of more than 20 organic compounds in the polycrystalline state over a broad temperature range in the frequency range 20–150 cm^–1. General features are found in the temperature dependence of the line frequencies and widths: coalescence of lines into bands, spectral blurring, intensity redistribution, etc. At liquid-nitrogen temperature the number of low-frequency lines is consistent with the Born theory, while at high temperatures (how high depends on the particular substance) the orientational disorder of a crystal strongly affects the spectrum.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 2, pp. 75–83, February, 1971.     

Vibrational relaxation and line widths in liquids dephasing by intermolecular forces

A theory of vibrational relaxation in liquids is presented in which the vibrations are loosely coupled to a bath or lattice of molecular translations and rotations by intermolecular forces. Using the second-order perturbation expressions familiar from magnetic resonance the secular contribution to the line width is calculated. Different coupling paths are considered and expressions given for the line widths in a liquid mixture in terms of number densities and diffusion coefficients valid when reorientation is slow and translation diffusional.     

Response of a cylindrical machine casing to oscillatory bearing forces

An analytical model is developed for the vibration response of a cylindrical machine casing excited by the force arising in a bearing that is assumed to support a rotating shaft. The casing system consists of a bearing housing mounted in a flat circular end cap that is built into a cylindrical casing. The housing is considered to be a rigid trunnion in the center of the end cap (which itself is modeled as a Mindlin plate). The development allows for arbitrary location of the center of mass of the housing and of the plane of action of the exciting force.     

Evolution of nuclear spectra with nuclear forces

We first define a series of NN interaction models ranging from very simple to fully realistic. We then present Green's function Monte Carlo calculations of light nuclei to show how nuclear spectra evolve as the nuclear forces are made increasingly sophisticated. We find that the absence of stable five- and eight-body nuclei depends crucially on the spin, isospin, and tensor components of the nuclear force.     

On the validity of the triple-dipole interaction as a representation of non-additive intermolecular forces

A complete partial wave analysis of the non-expanded non-additive coulomb interaction energy for three non-degenerate S-state atoms is given through third-order in the interatomic potential energy function. Pseudo state techniques are used to evaluate various partial wave components of the non-expanded second and third-order non-additive interaction energies for various isosceles triangular configurations of three interacting ground-state hydrogen atoms. These second and third-order non-expanded coulomb results are used, in conjunction with Heitler-London results for the first-order non-additive energies for the quartet spin state of the H(1s)-H(1s)-H(1s) interaction, to discuss the relative importance of various parts of the non-additive energy as a function of the geometrical configuration of the atoms, and the validity of both the non-expanded triple-dipole energy and the expanded Axilrod-Teller-Muto triple-dipole result as a representation of non-additive coulomb energies. For example, in the non-bonded interaction of three S-state atoms it appears that representing the non-additive energy by the non-additive coulomb energy is not reliable until the interatomic separations are somewhat larger than R*, the interatomic distance associated with the van der Waals minimum in the corresponding non-bonded dimer interaction. Further, the use of the triple-dipole interaction energy, with or without charge overlap corrections, to represent the non-additive coulomb energy is of doubtful validity until the interatomic separations are considerably greater than R*.     

Appearance of P-odd nuclear forces in photoproduction of pions on6Li

P-odd effects in the photoproduction of pions on⁶Li nuclei, +⁶Li ⁺ +⁶He, are studied. Collisions of linearly and circularly polarized photons with a polarized nuclear target are studied, and in addition both vectorial and tensorial polarization are taken into account. It is shown that in the general case P-odd effects in +⁶Li ⁺ +⁶He are characterized by 18 real structure functions, which determine different P-odd asymmetries in the angular distribution of the pions. The structure functions in their turn depend on different products of three p-even and three p-odd amplitudes of the process +⁶Li ⁺ +⁶He. The P-odd effects at the threshold of the reaction +⁶Li ⁺+⁶He are analyzed. Using available experimental data on the behavior of the cross section of the reaction +⁶Li ⁺ +⁶He at threshold, the ⁶Li⁶He strong-interaction constant is evaluated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 78–82 July 1985.     

Direct measurement of the intermolecular forces confining a single molecule in an entangled polymer solution

We use optical tweezers to directly measure the intermolecular forces acting on a single polymer imposed by surrounding entangled polymers (115 kbp DNA, 1 mg/ml). A tubelike confining field was measured in accord with the key assumption of reptation models. A time-dependent harmonic potential opposed transverse displacement, in accord with recent simulation findings. A tube radius of 0.8 microm was determined, close to the predicted value (0.5 microm). Three relaxation modes (approximately 0.4, 5, and 34 s) were measured following transverse displacement, consistent with predicted relaxation mechanisms.