Second harmonic intensity plots

Early studies were carried out at the liquid gas interface [22, 23]. Castro et al. [24] studied the adsorption of / -propyl-phenol from aqueous solutions at the air interface as a function of phenol concentration in the bulk. They showed that the square root of the second-harmonic intensity plotted against bulk phenol concentration followed a Langmuir isotherm with a standard Gibbs energy of adsorption equal to -24.3 kJmol Similar results were obtained for other alkylphenols and alkylanilines. In other work with phenols, the orientation of phenol at the water air interface was determined by studying the phase of the xfl component of the susceptibility. As expected, the OH was oriented toward the water phase [25] so that it could participate in the hydrogen-bonded structure of water. The same conclusion was reached for / -bromophenol and -nitrophenol. 

Fig. 5.24. Second harmonic intensity at 532 nm as a function of angle of rotation for Au(l 11) in 0.01 M H2S04 at (a) -0.1 V and (b) +0.7 V vs. SCE. s-polarized excitation and s-polarized SHG detection in both cases. For comparison purposes the calculated polar plots of the rotational anisotropies for s/s-polarization of a threefold symmetry surface with (a) and without (b) a onefold symmetry superimposed are also shown. From Ref. 156.

Fig.6a shows that the optical density, at the maximum optical absorbance wavelength = 376 nm, increases linearly with film thickness, up to approximately 0.4 pm. The linearity demonstrates that the film structure is independent of the number of deposited layers. When film thickness is further increased, the absorbance becomes so larg that the Lambert-Beer law is no longer satisfied. In Fig.6b the square root of the relative second-harmonic intensity is plotted versus the number of bilayers. 

The symmetry of the LB films was determined by polarized ultraviolet-visible (UV-Vis) absorption spectroscopy, optical rotation, and second-harmonic generation. All studies showed that the constructed LB films are anisotropic in the plane of the film and that the symmetry of the film is C2 with the twofold rotation axis perpendicular to the film plane. For example, when the SH intensity is plotted as a function of the azimuthal rotation angle (rotation around an axis perpendicular to the plane of the film), the twofold symmetry becomes evident (Figure 9.23). Isotropic films generate an SH signal independent of the azimuthal rotation angle. On the other hand, the LB... 

The frequency of modulation il is now the main parameter, and we are able to switch the system of SHG between different dynamics by changing the value of il. To find the regions of where a chaotic motion occurs, we calculate a Lyapunov spectrum versus the knob parameter il. The first Lyapunov exponent A,j from the spectrum is of the greatest importance its sign determines the chaos occurrence. The maximal Lyapunov exponent Xj as a function of is presented for GCL in Fig. 6a and for BCL in Fig. 6b. We see that for some frequencies il the system behaves chaotically (A-i > 0) but orderly Ck < 0) for others. The system in the second case is much more damped than in the first case and consequently much more stable. By way of example, for = 0.9 the system of SHG becomes chaotic as illustrated in Fig. 7a, showing the evolution of second-harmonic and fundamental mode intensities. The phase point of the fundamental mode draws a chaotic attractor as seen in the phase portrait (Fig. 7b). However, the phase point loses its chaotic features and settles into a symmetric limit cycle if we change the frequency to = 1.1 as shown in Fig. 8b, while Fig. 8a shows a seven-period oscillation in intensities. To avoid transient effects, the evolution is plotted for 450 < < 500. 

Using the technique described earlier [83] to get samples that are nearly monodomain, second harmonic generation has been investigated using a Q-switched Nd-YAG laser [85]. Since the helix is unwound in these samples and since they are close to a monodomain, they are macroscopically of Cj-symmetry and thus suitable for second harmonic generation. In Fig. 28 the intensity of the second harmonic signal is plotted as a function of the angle around the direction in the plane of the film, which is perpendicular to the first deformation direction. The results of the polarization dependent measure-... 

Fig. 13. Left The temperature-humidity phase diagram of DMPC. Because both axes are related to thermodynamic potentials, there are no two-phase regions. Note that the phase previously known as Lp is, in fact, three distinct phases, L p, L l, and L j. Right Log-log plot of the scattering intensity from the tails of the first and second harmonics of the ternary mixture [SDS (30% by weight) pentanol (23%), water (47%)] and the sixth harmonic of DMPC-water (90% RH, 31 C).

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