Quadrupole moment polarizability measurements

Birefringences are mostly observed in condensed phases, especially pure liquids or solutions, since the strong enhancement of the effects allows for reduced dimensions (much shorter optical paths) of the experimental apparatus. Nowadays measurements of linear birefringences can be carried out on liquid samples with desktop-size instruments. Such measurements may yield information on the molecular properties, molecular multipoles and their polarizabilities. In some instances, for example KE, CME and BE, measurements (in particular of their temperature dependence) have been carried out simultaneously on some systems. From the combination of data, information on electric dipole polarizabilities, dipole and quadrupole moments, magnetizabilities and higher order properties were then obtained. 

Dielectric and pressure virial coefficients of NzO have been measured at 6.5, 30.1, and 75.1 °C. The dipole moment, polarizability, and molecular quadrupole moment were determined to be 0.18 D, 3.03 x 1CT24 cm3, and 3.4 xlO 26 e.s.u. cm2, respectively.91 A lower limit of —0.15 0.1 eV has been calculated for the molecular electron affinity of N20, using molecular beam studies.92 The enthalpy-pressure behaviour for N20 along eleven isotherms in the vapour phase has been determined from measurements of the Joule-Thomson effect.91... 

The experimental importance of the BE is due to the fact that it allows the experimental determination of molecular electric quadrupole moments . The procedure is based on Eq. (34) and was first proposed by Buckingham [134] in the late fifties. With the assumption that the molecular polarizability is known, can be extracted from measurements of An. In order to separate the Ag from the Aj contribution, it is necessary to perform BE measurements over an appropriately large temperature range. 

More recently, Ritchie, Watson and Keir [170] carried out new experiments on the BE of Nj for a variety of different temperatures, thus enabling a proper separation of the temperature-independent contribution from the orientational term. These authors also performed new measurements for Are polarizability anisotropy. Combining all their experimental data, they were able to extract a new experimental value of (-4.97 0.16) x 10 ° Cm for the quadrupole moment of N2. The good agreement with tire previous (with the CCSD result) revised experimental value as well as the corresponding theoretical results (see Table 13) clearly eliminates any remaining doubts concerning the experimental quadrupole moment of N2. 

Experimental measurements of Aie BE can also be used to determine quadrupole moments for dipolar systems. The values obtained in this way refer to an origin which is denoted as the effective quadrupole center (EQC) [135]. The EQC is defined as Aie point at which the combinaAon of dipole-quadrupole and dipole-magnetic dipole polarizabilities multiplied with the dipole moment given in Eq. (27)... 

Wheeler 2 has pointed out that further information about the nucleus can be obtained from more precise measurements of the X-ray spectrum especially of the fine structure that should be present. The things that one can study include nuclear quadrupole moments, the non-uniformity of the nuclear charge distribution, and nuclear polarizability. 

David and Person (1968) measured the absolute infrared intensities of the translational lattice modes of the solid halogens. They did not carry out a complete calculation adapted to the crystal structure of these solids. These authors found, however, very good correlation between the measured absolute intensities and the molecular properties, i.e., quadrupole moments and polarizabilities, as expected from the theory. 

The first term in this series is obviously just the permanent dipole moment of the molecule. The coefficient of the second term is the polarizability of the molecule, which measures the change in dipole moment induced by the external field. Higher terms in the series will yield higher hyperpolarizabilities. Analogous expressions may be derived for the quadrupole moment. 

Method of moments. In rare gas mixtures, the induced dipole consists of just one B component, with Ai AL = 0001, Eq. 4.14. Alternatively, one particular B(c) component may cause the overwhelming part of a measured spectrum, like the quadrupole-induced component in mixtures of small amounts of H2 in highly polarizable rare gases ((c) = Ai AL = 2023, Eq. 4.59) in a given spectral range, other components (like 0001, 2021,...) are often relatively insignificant. In such cases, one can write down more or less discriminating relationships between certain spectral moments of low order n that are obtainable from measurements of the collision-induced spectral profile, g Al(o>),... 

The polarity of the molecules is usually considered to be measured on a gross scale by the relative permittivity and on a molecular scale by the electrical dipole and higher moments. Molecules lacking a dipole moment (carbon dioxide, for example) may still exert short-range effects due to quadrupole, and so on, moments. Dipolar bonds that are well separated in a molecule may act almost independently on neighboring molecules Hildebrand and Carter (1930) showed that the three isomeric dinitrobenzenes, in their binary solutions in benzene, exhibit nearly identical deviations from Raoult s law, though their dipole moments are different. The part of the electrical influence of a solvent on solute molecules that arises from the polarizability of the solvent molecules may be represented by the refractive index, n, or by functions of n such as the volume polarization, R, given by ... 

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