Hyper-Rayleigh scattering

Although, a priori, there are a large number of /I tensor components intervening in Eqs. (9)-(12) for the limited amount of experimental data, their number is usually limited by molecular symmetry and Kleinmen conditions. Moreover, some of the components can be neglected with respect to others. 

The P tensor components are obtained from the slope of the scattered light intensity at harmonic frequency versus the square of the fundamental beam intensity, measured for different polarization configurations. The value of the g parameter intervening in Eqs. (9)-( 11) is obtained by calibration with a solvent of known /lvalue. These HRS measurements have to be done very carefully, as other processes such as two-photon-induced fluorescence, Raman, and higher order NLO processes can contribute to the measured HRS signal. Actually, the use of the time-re-solved technique with femtosecond pulses allows for the separation of photons coming from the harmonic generation of the others. 

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An important goal of this study is to characterize the noncentrosymmetric arrangement of the azobenzene branches in dendrimers and the effect of these dendrimers on macroscopic second-order susceptibihty. The NLO activity of the dendrimers can be characterized by their molecular hyperpolarizabihty. The hyper-Rayleigh scattering (HRS) method is a reliable way of measuring the mol-... 

Cp Ru[H5C5B-C=C(C5H4)FeCp]+ nonlinear optics application S, X, H, C, IR, UV, E, hyper-Rayleigh scattering 20... 

The ethynyl-linked complexes 105 were prepared and explored as potential building blocks for nonlinear optical (NLO) materials.129 Spectroscopic and cyclic voltammetry data indicate a small but real interaction between the ferrocenyl donor group and the borabenzene unit, increasing in the order Rusmall values for the first hyperpolarizability / , which increases in the same order. 

Abstract Second-order nonlinear light scattering, or hyper-Rayleigh scattering (HRS)... 

Keywords nonlinear optics, hyperpolarizability, hyper-Rayleigh scattering, photonic crystals, photonic bandgap materials... 

When a non-centrosymmetric solvent is used, there is still hyper-Rayleigh scattering at zero solute concentration. The intercept is then determined by the number density of the pure solvent and the hyperpolarizability of the solvent. This provides a means of internal calibration, without the need for local field correction factors at optical frequencies. No dc field correction factors are necessary, since in HRS, unlike in EFISHG, no dc field is applied. By comparing intercept and slope, a hyperpolarizability value can be deduced for the solute from the one for the solvent. This is referred to as the internal reference method. Alternatively, or when the solvent is centrosymmetric, slopes can be compared directly. One slope is then for a reference molecule with an accurately known hyperpolarizability the other slope is for the unknown, with the hyperpolarizability to be determined. This is referred to as the external reference method. If the same solvent is used, then no field correction factor is necessary. When another solvent needs to be used, the different refractive index calls for a local field correction factor at optical frequencies. The usual Lorentz correction factors can be used. 

The experimental set-up for femtosecond hyper-Rayleigh scattering is in essence identical to the one for the nanosecond experiments.9 Only the gated integrators for the nanosecond measurements are replaced by a chopper and a phase-sensitive detector in the high-frequency femtosecond experiment. 

Based on these results for the ethenylene, butadienelyne and hexatrienylene linkage, we have varied the substitution pattern in combination with the butadienylene linkage. The additional compounds that were available are identified as 21 22 23 and 24. The experimental values for the first hyperpolarizabilities have all been determined by femtosecond hyper-Rayleigh scattering with high-frequency demodulation of the two-photon fluorescence, both at 800 nm and at 1300 nm. All the stilbazolium... 

Figure 4. Open circles, angular dependence of the second-order scattered light intensity (hyper-Rayleigh scattering from 1064 to 532 nm) for a suspension of purple membrane patches of bacteriorhodopsin before any solubilization has taken place. Solid curve best fit to the data by combining the nonlinear hyperpolarizability of retinal with the linear refractive index of the upo-protein.

Gold nanoparticles have large second- and third-order nonlinear susceptibilities and are therefore a promising class of nonlinear optical materials.214 We will briefly discuss several nonlinear optical processes from metal nanoparticles, such as multiphoton luminescence, hyper-Rayleigh scattering, and multiharmonic generation. 

Aminovinylnitrothiophenes 84, a novel type of push-pull chromophores, were closely investigated with respect to their NLO and thermal properties [82]. Hyper-Rayleigh scattering (HRS) measurements at a fundamental of 1500 nm re-... 

When the sample is illuminated by a giant pulse of frequency v, the scattered radiation contains frequencies of 2v (hyper-Rayleigh scattering) and 2v vm (Stokes and anti-Stokes hyper-Raman scattering), where vM is a frequency of a normal vibration of the molecule. Clearly, this is Raman scattering caused by two incident photons (2v) of the laser. Experimentally, this... 

The different symmetry properties considered above (p. 131) for macroscopic susceptibilities apply equally for molecular polarizabilities. The linear polarizability a - w w) is a symmetric second-rank tensor like Therefore, only six of its nine components are independent. It can always be transformed to a main axes system where it has only three independent components, and If the molecule possesses one or more symmetry axes, these coincide with the main axes of the polarizability ellipsoid. Like /J is a third-rank tensor with 27 components. All coefficients of third-rank tensors vanish in centrosymmetric media effects of the molecular polarizability of second order may therefore not be observed in them. Solutions and gases are statistically isotropic and therefore not useful technically. However, local fluctuations in solutions may be used analytically to probe elements of /3 (see p. 163 for hyper-Rayleigh scattering). The number of independent and significant components of /3 is considerably reduced by spatial symmetry. The non-zero components for a few important point groups are shown in (42)-(44). 

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