Molecules quadrupolar

Bhowmik P K and Su T 1986 Tra]ectory calculations of ion-quadrupolar molecule collision rate constants J. Chem. Phys. 84 1432-4... 

Restricting the sum-over-states equations, which in general cases need to include all states of the system [91,92], to include only terms relating to three states of a quadrupolar molecule, the groimd state (g), the lowest one-photon allowed excited state (e), and the lowest two-photon-allowed state (f), which are the states depicted in Fig. 1 when / = e, the maximum two-photon cross section can be expressed as follows [93,94] ... 

Fig. 8 Schematics of various linear (one-dimensional) chromophores classified based on the substitution pattern. I-IV quadrupolar molecules V dipolar molecules (D = donor group 7T = 7T-conjugated bridge A = acceptor group)...

Table 3 2PA properties of quadrupolar molecules with various types of jr-bridges. The solvent in which the measurement was performed is indicated in parenthesis after the molecular structure ( )... 

We use a very simple example, consisting of a dipolar and quadrupolar molecule interacting with a polarizable atom. The molecule is of cylindrical symmetry yet has the dimensions and the long-range electrical and inertial properties of H2O the atom is akin to atomic H. Because of the (supposed) cylindrical symmetry and because of the great simplification it entails, we restrict ourselves to a planar problem. 

Quadrupolar molecules. In a first approximation, we can assume the molecular electric fields to polarize the molecules isotropically, enabling us to write (199) for molecules of a single species, and on neglecting anisotropy (d = 0) ... 

Quadrupolar molecules. In a liquid composed of anisotropic non-polar molecules, the molar constant (291b) is still applicable in a first approximation (it defines the contribution from fluctuations in number density of the molecules, as in isotropic light scattering. The anisotropic molar constant (292) reduces to the contribution ... 

For quadrupolar molecules, the dipole contribution (294) is non-zero also, since... 

Jb) Amsotropic quadrupolar molecules. In dealing with non-dipolar molecules, we have to consider only the parameter which, on taking into account anisotropic London dispersional interactions [equation (90a)], is of the form ... 

S. Kielich, J. R. Lalanne, and F. B. Martin, second harmonic light scattering induced in liquids by fluctuational electric fields of quadrupolar molecules. Acta Phys. Polonica, A, 47 479 82 (1972). 

A few comments on Table 5.2 seem appropriate at this point. CO has such a small dipole moment C 0+ that can be considered a quasi-quadrupolar molecule. NH3 has large axial quadrupole and octupole moments directed along the z symmetry axis. Besides by its dipole moment, H2O is characterized by a rather small (0.06< uo2) axial quadrupole moment and by a large transverse quadrupole moment (2.19e o2) perpendicular to the z symmetry axis, mostly due to the couple of lone pair electrons. LiH has the largest dipole moment and dipole polarizability. 

Abstract The first part of this review presents the state of the art on two-photon absorbing molecules. Early works concerned the optimization of dipolar push-pull molecules. Recently, the synthesis of linear and branched centrosymmetrical quadrupolar molecules led to higher nonlinearities, but still far from reaching the fundamental limits of molecular two-photon cross-sections. 

Fig.1 Schematic representation of dipolar and quadrupolar molecules (A and D represents, respectively, electron acceptor and donor)...

The structure of quadrupolar molecules is generally noted as D-n-D or A-7t-A (see Fig. 1). For these molecules, the term Ayxoi of the relationship Eq. 5 cancels and this equation can be rewritten as Eq. 7, and molecules fulfill the three-level model represented in Fig. 2a. 

This work led to many molecular engineering investigations on quadrupolar molecules for TPA [72-88]. Quadrupolar polyenes have been theoretically... 

Rainwater and his co-workers have extended their work on heteronuclear hard dumbbells to the treatment of dipolar systems [267]. They have used a generalized van der Waals theory similar to that used for quadrupolar molecules [152,266] to calculate the phase diagram and have compared their results with experiment for methyl chloride. The theory correctly predicts the effect of the dipole moment on the stable crystal structure. 

The leading term in the electrostatic interaction between a pair of linear, quadrupolar molecules, such as HCCH and CO2 is... 

For interactions between two quadrupolar molecules which have and 0g of the same sign, at a fixed separation r, the angular factor in equation (Al. 5.13) leads to a planar, T-shaped structure, 0 = 0, 0g = 7i/2, ( ) = 0, being preferred. This geometry is often seen for nearly spherical quadrupolar molecules. There are other planar (( ) = 0) configurations with 0 = 7i/2-0g that are also attractive. A planar, slipped parallel structure,... 

For interactions between tw o quadrupolar molecules which have 0 and 0g of the opposite sign, at a fixed separation r. the ansular factor in equation t A1.5.13) leads to a linear structure. A B being the most attractive. Linear molecules may also prefer a rectangular or non-planar cross arrangement with B... 

Figure 3 Schematic representation of a regular periodic arrangement of like quadrupolar molecules...

---