A. Asenbaum

A Raman spectroscopic approach to the maturation process of fossil resins

Raman spectra of a range of differently aged samples of natural resins (recent resins, copals, fossils resins from Tertiary to Early Cretaceous age) were taken for a comparative study of the age-induced maturation processes of the resins. It can be shown that a decrease in band intensity at around 1640 cm−1 due to loss of ν(CC) stretching vibrations, together with other spectral details, is correlated with the increase in age of the resins. Copyright

The non-coincidence effect in highly diluted acetone-CCl I. Experimental results and theoretical predictions 4 binary mixtures

The concentration dependence of the first moments and peak frequencies of isotropic and anisotropic profiles of the υC=O mode in acetone–CCl4 binary mixtures is investigated. The emphasis is directed mainly towards the non-coincidence effect in the high dilution range, not accessed in previous experiments. Our results for the relative non-coincidence effect in non-isotopic binary mixtures appear largely consistent with the Logan theory. Moreover, the observation of the υC=O mode of the naturally present acetone–13C=O has been exploited to check the validity of the Logan theory for isotopic mixtures. It is verified that the observation of negative values for the non-coincidence effect, which is strictly related to that of a threshold concentration for the onset of this phenomenon, are artefacts due to the presence of spectral asymmetries in the υC=O mode.

The non-coincidence effect in N,N-dimethylformamide-CCl4 highly diluted binary mixtures. Experimental and theoretical results

We report results on the concentration dependence of the non-coincidence effect in the v(C=O) mode in N,N-dimethylformamide-CCl4 mixtures. This study has been mainly addressed to the investigation of the experimentally observed sign inversion for this quantity in the low concentration range of chemical mixtures, which is also reported in the literature. We argue that the sign inversion of the non-coincidence effect in N,N-dimethylformamide-CCl4 mixtures is an artefact originated by the presence of an intrinsic asymmetry which with dilution moves from the blue to the red side of the band. The Logan theory for the thermodynamic state dependence of the non-coincidence effect in chemical mixtures offers a valuable tool for the interpretation of the results in the whole concentration range. Different models are compared and discussed.

Interferometric determination of the refractive index of liquid sulphur dioxide

The absolute refractive index of liquid sulphur dioxide (SO2) was determined with an uncertainty of ±0.0007 with the help of a Michelson interferometer and a computer-controlled rotatory stage supporting a rectangular fused silica cell, containing the liquid. The measurements were performed at temperatures around 20 °C for the laser line wavelengths 632.8, 514.5 and 488.0 nm. The experimental data were fitted to the simple Cauchy dispersion formula. The results calculated from this formula are consistent within the experimental uncertainty with published values obtained at other wavelengths and/or other temperatures.

Mid-infrared absorptance of silicon hyperdoped with chalcogen via fs-laser irradiation

Silicon hyperdoped with heavy chalcogen atoms via femtosecond-laser irradiation exhibits strong broadband, sub-bandgap light absorption. Understanding the origin of this absorption could enable applications for hyperdoped-silicon based optoelectronic devices. In this work, we measure absorption to wavelengths up to 14 μm using Fourier transform infrared spectroscopy and study sulfur-, selenium-, and tellurium-hyperdoped Si before and after annealing. We find that absorption in the samples extends to wavelengths as far as 6 μm. After annealing, the absorption spectrum exhibits features that are consistent with free-carrier absorption. Although the surface morphology influences the shape of the absorption curves, the data permit us to place an upper bound on the position of the chalcogen dopant energy levels.

Polarized light scattering from density fluctuations in liquid carbon disulfide

Abstract Polarized light scattered from density fluctuations in liquid carbon disulfide was measured for different scattering angles ranging from 45 to 172 degrees. The theory of Mountain, containing a relaxing bulk viscosity (MOUETA), the theory of Mountain, based on an internal relaxing degree of freedom (MOUXI), and the translational hydrodynamic theory of Desai and Kapral (TH), including diffusion effects, were fitted to the experimental spectra. Agreement was found between all three theories and the experiment at small wave vectors k. At high values of k, however, only the theories MOUXI and TH are consistent with the experiment. Since TH and MOUXI become identical in the limit of vanishing diffusion, this shows, that diffusion effects can be neglected in polarized light scattering at liquid state densities.