Induced dipole correlation effects

The comparison of spectral line shapes computed on the basis of the ab initio dipole surface of He-Ar with absorption measurements has demonstrated the soundness of the data. The agreement indicates that exchange effects due to intra-atomic correlation and higher-order dispersion terms contribute significantly to the induced dipole. However,... 

H2 quadrupole moment, <72(re) at the fixed equilibrium position, and thus the long-range coefficient of the quadrupole-induced dipole component, Eq. 4.3, is about 5% too small relative to the proper vibrational average, <12 = (v = 0 < 2(r) f = 0) [216, 217, 209], A 5% difference of the dipole moment amounts to a 10% difference of the associated spectral intensities. Furthermore, the effects of electron correlation on this long-range coefficient can be estimated. Correlation increases the He polarizability by 5% but decreases the H2 quadrupole moment by 8% [275], a net change of-3% of the leading induction term B R). 

Recent work improved earlier results and considered the effects of electron correlation and vibrational averaging [278], Especially the effects of intra-atomic correlation, which were seen to be significant for rare-gas pairs, have been studied for H2-He pairs and compared with interatomic electron correlation the contributions due to intra- and interatomic correlation are of opposite sign. Localized SCF orbitals were used again to reduce the basis set superposition error. Special care was taken to assure that the supermolecular wavefunctions separate correctly for R —> oo into a product of correlated H2 wavefunctions, and a correlated as well as polarized He wavefunction. At the Cl level, all atomic and molecular properties (polarizability, quadrupole moment) were found to be in agreement with the accurate values to within 1%. Various extensions of the basis set have resulted in variations of the induced dipole moment of less than 1% [279], Table 4.5 shows the computed dipole components, px, pz, as functions of separation, R, orientation (0°, 90°, 45° relative to the internuclear axis), and three vibrational spacings r, in 10-6 a.u. of dipole strength [279]. 

Model correlation functions. Certain model correlation functions have been found that model the intracollisional process fairly closely. These satisfy a number of physical and mathematical requirements and their Fourier transforms provide a simple analytical model of the spectral profile. The model functions depend on the choice of two or three parameters which may be related to the physics (i.e., the spectral moments) of the system. Sears [363, 362] expanded the classical correlation function as a series in powers of time squared, assuming an exponential overlap-induced dipole moment as in Eq. 4.1. The series was truncated at the second term and the parameters of the dipole model were related to the spectral moments [79]. The spectral model profile was obtained by Fourier transform. Levine and Birnbaum [232] developed a classical line shape, assuming straight trajectories and a Gaussian dipole function. The model was successful in reproducing measured He-Ar [232] and other [189, 245] spectra. Moreover, the quantum effect associated with the straight path approximation could also be estimated. We will be interested in such three-parameter model correlation functions below whose Fourier transforms fit measured spectra and the computed quantum profiles closely see Section 5.10. Intracollisional model correlation functions were discussed by Birnbaum et a/., (1982). 

The analysis of the dipole moment curves for the motion of the adsorbate perpendicular to the surface provides additional information about the degree of ionicity of a given surface chemical bond. Moreover, the analysis of the dipole moment curves is also related to the interpretation of variations of the surface work function induced by the presence of the adsorbate. However, the response of the surface to the presence of the adsorbate does not permit to extract directly adsorbate charges from the dipole moment curve. A procedure based in the use of frozen densities has been proposed that permits to avoid the effect of the surface polarization on the dipole moment curve. Unfortunately, this method has not been yet extensively used. To close this short discussion about the different procedures commonly used to interpret the chemical bond between chemical species and the surface of a catalyst in terms of net charges we mention the valence bond reading of Hartree-Fock and Configuration Interaction wave functions. This procedure has been used to interpret the electronic correlation effect on the surface chemical bond. ... 

Here, we report, for the first time, ab initio computations of the six lowest-lying electronic states of Na2" ". These computations utilize the basis set developed to describe the low-lying states of the neutral Nap, molecules (6) and utilize integrals which have been computed previously (, ). The molecular energies computed at the single-configuration self-consistent-field (SC-SCF) level are listed in Table I. These SC-SCF computations should provide relatively reliable potential curves for what are effectively one-electron systems. We do not attempt to describe the electron correlation associated with the core electron motions nor that associated with the polarization of the core electrons by the single valence electron. Thus, while dispersion effects are not well described, the first order ion-induced dipole Interaction and the major electrostatic interactions of the valence electron are probably reasonably well described at the SC-SCF level. Note in Table II, where we list molecular constants for Nap, that the 1 state is bound. Its 1 T. counterpart in the neutral molecule is predicted to be... 

Most of the potential energy surfaces reviewed so far have been based on effective pair potentials. It is assumed that the parameterization is such as to account for nonadditive interactions, but in a nonexplicit way. A simple example is the use of a charge distribution with a dipole moment of 2.ID in the ST2 model. However, it is well known that there are significant non-pairwise additive interactions in liquid water and several attempts have been made to include them explicitly in simulations. Nonadditivity can arise in several ways. We have already discussed induced dipole interactions, which are a consequence of the permanent diple moment and polarizability of the molecules. A second type of nonadditive interaction arises from the deformation of the molecules in a condensed phase. Some contributions from such terms are implicitly included in calculations based on flexible molecule potentials. Other contributions arises from electron correlation, exchange, and similar effects. A good example is the Axilrod-Teller three-body dispersion interaction ... 

The Stark effect on the magnetic fine structure occurs as a result of disturbance of atomic levels under the influence of the relativistic and correlation effects as well as the interaction with external electric field F. If the fields are weak enough the centre of multiplet is shifted and there occurs the splitting of sublevels of atomic multiplet n, L, J. The dipole moment induced in an atom by a uniform electric field F is for most purposes expressed as a linear function of F, but higher... 

Abstract We consider a possible realization of the position- and momentum-correlated atomic pairs that are confined to adjacent sites of two mutually shifted optical lattices and are entangled via laser-induced dipole-dipole interactions. The Einstein-Podolsky-Rosen (EPR) "paradox" [Einstein 1935] with translational variables is then modified by lattice-diffraction effects. We study a possible mechanism of creating such diatom entangled states by varying the effective mass of the atoms. 

The effect of cationic polyacrylamide adsorption on the stability of aqueous cellulose suspension has been electro-optically studied by Khlebtsov et al. [19,20], The variations in transmitted light modulation in low-frequency (3-45 Hz) square-pulsed a.c. fields have been found to correlate well with the adsorption isotherm. The influence of sodium carboxymethylcellulose adsorption on the electro-optical behavior of negatively charged Si02 (ani-sometric aggregates, consisting of monodisperse spherical particles) has also been studied, and an increase of the particle induced dipole moment and its time of relaxation has been found [21,22],... 

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