Polarizability nonlinear

We now consider this issue in a more rigorous fashion. The inference of molecular orientation can be explamed most readily from the following relation between the surface nonlinear susceptibility tensor and the molecular nonlinear polarizability... 

The approach may be illustrated for molecules with a nonlinear polarizability aP dominated by a single axial component ct P., corresponding to a dominant nonlinear response from transitions along a particular... 

As an example, the model described earlier for a molecule havmg a dominant nonlinear polarizability element... 

Nonintuitive Light Propagation Effects In Third-Order Experiments. One of the first tasks for a chemist desiring to quantify second- and third-order optical nonlinear polarizability is to gain an appreciation of the quantitative manifestations of macroscopic optical nonlinearity. As will be shown this has been a problem as well for established workers in the field. We will present pictures which hopefully will make these situations more physically obvious. 

New THG Methods For Molecular Liquid Characterization. An area which is essential for understanding general third-order nonlinear polarizability is characterization of the purely electronic contributions (48). Several methods have been employed for this... 

A novel second-order nonlinear optical medium which should offer considerable fabrication flexibility has been described. The physics of alignment of the highly nonlinearly polarizable moiety was discussed. However, observation of complex dynamical and thermal behavior indicates that an important role is played by the polymer liquid crystalline host. Additional properties of modified members of this family of lc polymers were consequently investigated. The explanations of guest alignment stabilization and thermal dependence of the alignability remain unresolved issues. 

For larger displacement UA-, the variation of i(r, r ) relative to UK can be computed by using the nonlinear polarizability kernels defined below [26] (see Section 24.4). Forces and nonlocal polarizabilities are thus intimately related. 

Equation 24.110 permits to formulate the nonlinear dipole hardness /z3 of an atom in an electric field (Equation 24.18) in terms of the responses n- We assume a field applied along the x Cartesian direction. The nonlinear polarizability a3 (Equation 24.10) is... 

From the nonlinear polarizability model it can be inferred that / > g2 and consequently o > 0. This means that the coupling C leads to an increase in Tc and, since C Idkdp > C kdp the transition temperature is larger for DKDP than for KDP. The direct proton-proton coupling is negligible for any Tc enhancement effects, while the interaction that is mediated by the coupling between the PO4 shells and the protons is essential. 

The data have been analyzed within the described coupled double-well model. The protons are represented by pseudospins whereas the C4O4 unit displays highly nonlinear polarizability effects, which are taken into account within the framework of the nonlinear polarizability model [17,20]. As compared to KDP-type ferroelectrics the model is less complex [26,27] since the... 

Optical second harmonic generation (SHG), which stems from the conversion of two photons of frequency to to a single photon of frequency 2(o, is an inherently surface-sensitive technique. Whereas no optical second harmonic wave is generated in the centrosymmetric bulk of a liquid, molecules participating in the asymmetry of the interface between two liquids (noncentrosymmetric environ-ment) contribute to SHG. Since the square root of SHG signal intensity, is proportional to the number N (per unit area), the molecular orientation (I) and the second order nonlinear polarizability of the SHG active species at the interface... 

The simplest description of compoimds of this type is obtained limiting the siun-over-state equations to terms depending only on the properties of the groimd state g and the first excited state e (two-state model) [93]. This is analogous to the two-level model introduced to describe other nonlinear optical properties, for example the nonlinear polarizability pS - co coi,co2) [ 104]. In the case of 2PA, this two-state, or dipolar, contribution to the cross section is, on resonance ... 

Finally, the nonlinear polarizability of dyes is used for frequency tripling the output of high-power lasers. 

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