Three imidazolium-based ionic liquids of the type [C n mim][NTf 2 ] with different alkyl chain lengths (n = 1, 2 and 8) at the first position of the imidazolium ring were studied applying infrared, linear Raman and multiplex coherent anti-Stokes Raman scattering spectroscopy. The focus has been on the CH-stretching region of the imidazolium ring, which is supposed to carry information about a possible hydrogen bonding network in the ionic liquid. The measurements are compared with calculations of the corresponding anharmonic vibrational spectra for a cluster of [C 2 mim][NTf 2 ] consisting of four ion pairs. The results support the hypothesis of weak hydrogen bonding involving the C(4)-H and C(5)-H groups and somewhat stronger hydrogen bonds of the C(2)-H groups.

Lateral diffusion of three different dye molecules (terrylene and two perylene diimides) in 4 to 225 nm thin films of 8CB liquid crystals in the smectic-A phase has been investigated on a single molecule level. The influence of film thickness on tracer diffusion can be qualitatively modeled by a hydrodynamic approach. Molecular tracking experiments as well as fluorescence correlation (FCS) studies reveal the presence of diffusion dynamics which span a range of at least more than one order of magnitude in time, which is much larger than the reported anisotropic self-diffusion observed for 8CB bulk samples. We tentatively assign the heterogeneity to the formation of diffusion limiting domains on a micrometer scale within the 8CB films or at the interfaces.

This article reports an efficient method to simulate time and frequency resolved coherent anti‐Stokes Raman scattering spectra measured with picosecond pump and probe fields and ultrashort Stokes pulses. A systematic comparison of measured and simulated time and frequency dependent data is presented for carbon tetrachloride, chloroform, cyclohexane, octane, and poly(methyl methacrylate). While the first compound exhibits no Raman active modes in the considered spectral region of the CH‐stretch vibrations, the other ones show Raman spectra of increasing complexity. Vibrational frequencies and homogeneous dephasing rates are extracted by fitting explicit analytical formulas to the recorded data. Interference between nonresonant and resonant contributions to the nonlinear polarization is taken fully into account. The ability to measure the influence of inhomogeneous broadening is discussed. Copyright © 2014 John Wiley & Sons, Ltd.

We present a comparison of spontaneous Raman and ultrafast coherent anti-Stokes Raman scattering (CARS) spectra of the C=O vibration of liquid acetic acid. The former technique cannot clearly reveal the number of contributions in the spectrum. However, the additional time and spectrally resolved CARS experiment supports strictly the existence of four modes, which proves the coexistence of more than one H-bonded configuration in liquid acetic acid. A comparably slowly dephasing mode which is obscured by a broad band in the linear Raman spectrum is assigned to the cyclic dimer and can be observed freed from all other contributions by ultrafast CARS.