The Role of Intermolecular Interactions in the Electro-Optical Kerr Effect in Liquid Alkanes

Abstract

The electro-optical Kerr effect of n-alkanes from C 5 to C 16 was investigated in gas phase, liquid phase, and solution. The values of the Kerr constants in gas phase are noticeably distinguishable from those in liquids, where the molecules interact by the London dispersion forces. Both the energy of the dispersion interaction and the difference in the Kerr constants in liquid and gas phase grow with molecular size, indicating the key influence of the interaction on the magnitude of the Kerr effect. Several orientation and molecular-statistical theories of electro-optical Kerr effect were applied to model the change in electro-optical Kerr effect due to the dispersion force. Most theories show significant divergence compared to the experimental data. It is argued that the decisive contribution to electro-optical Kerr effect in liquids and the deviations between the experiment and theory arise due to local liquid structures that collectively orient in the external electric field.

Polarity of Hydrated Phosphatidylcholine Headgroups

“…Fits of Model Polarity Functions to the Data. The results of the calibration of the dependencies of indole and Nile Red absorption and fluorescence peak wavelengths on the dielectric constants 44,71,72 and the refractive indices (eqs 1−5) are shown in Figure 1A,B for indole and Nile Red, respectively, and summarized in Table 2. The error bars of the wavelength terms in Figure 1A,B are not shown because the standard errors of the means (SEMs) of the peak wavelengths (Table 1) lead to the errors of the wavelength terms, which are smaller than the diameter of the shown points.…”

“…The results of the calibration of the dependencies of indole and Nile Red absorption and fluorescence peak wavelengths on the dielectric constants 44,71,72 1) lead to the errors of the wavelength terms, which are smaller than the diameter of the shown points. The errors range from 2.3×10 −6 nm −1 to 1.3×10 −5 nm −1 for indole (Figure 1A), and from 4.2×10 −7 nm −1 to 3.6×10 −6 nm −1 for Nile Red (Figure 1B).…”

“… a All data for 25 °C, unmarked polarity indices from ref . b The values extrapolated from methanol/water data because of low solubility. c From ref . d The value was not available, so the value for n -dodecane was used, which was identical to, or only slightly different from, the values for alkanes from n -pentane to n -decane …”

Solute−Solvent Interactions Determine the Effect of External Electric Field on the Intensity of Molecular Absorption Spectra

“…Early measurements have shown that the effect is usually small, although it cannot be neglected . Ground state DMs are commonly used for characterization of electronic charge distributions in molecules , and solute−solvent interactions. − DMs of molecules in excited electronic states are more difficult to obtain. For this purpose one can use the dependence of optical absorption lines on the external electric field .…”