With the use of the Maxwell Garnett (MG) approximation and of the developed combined model of an effective medium (CMEM), we have investigated the spectral and concentration dependences of the real (neff) and imaginary (keff) parts of the complex effective refractive index of the Ag−C60 and Cu−C60 nanostructures in the visible range, as well as the dependence of their electrical conductivity in the near IR spectral region on the concentration of components. By comparing the results of theoretical calculations of the optical density with experimental data for the Ag−C60 and Cu−C60 composites produced by thermal vaporization and vacuum condensation it has been established that the CMEM has advantages over the MG approximation. The experimentally observed nonmonotonic spectral dependence of the optical density maxima of Cu−C60 composites coincides well with the CMEM-based calculations. Moreover, the application of this model made it possible to determine the percolation threshold in the near IR region for the nanostructures investigated.

For planar nanocomposites Ag-LiF fabricated by the thermal vacuum evaporation and characterized by a high volume part of a metal phase (p = 0.6-0.8), the concentration features of the surface plasmon absorption band were analyzed. Based on the probabilistic approach to the description of a nanocomposite structure, the new combined model of the effective medium is proposed, which takes into account the matrix inversion at the metal concentration increase over p=0.5. The model describes well the experimental data.

A new mixing rule for the effective dielectric constant of composite materials is formulated on the basis of a probabilistic approach for describing the structure of granular composite structures. The advantages of the proposed model become apparent for high concentrations of inclusions with optical constants that differ significantly from those of the matrix. The distinctive feature of this model compared to the Maxwell Garnett rule is symmetry of the computational formulas and their invariance with respect to the numbering order of the materials, as well as the possibility of describing the two-mode structure of the surface plasmon resonance absorption band in metal-dielectric nanocomposites with a high concentration of the metallic phase.

Conformations of He-jet-cooled trimethyl[(3-indole)ethoxy]silane (TIES) have been studied using a laser spectroscopy technique in combination with quantum-chemical computations. Six probable conformers of the molecule were computed, of which only two conformations were observed. Based on an analysis of fluorescence excitation spectra, fluorescence spectra, shapes of rotational band contours at the electronic S0–S1 transition of TIES, and theoretical computations, the above conformers were assigned to steric structures. Twisted structures have the lowest energy due to intramolecular hydrogen bonds \( C - H \cdots O <_C^{Si} \) between hydrogen atoms of methyl groups and an oxygen atom and C–H···π between H and the π-electron cloud of the indole ring.

The rotational contours of the bands corresponding to electronic and electronic-vibrational transitions of the fluorescence excitation spectrum of jet-cooled carbazole complexes with one, two, and three water molecules have been studied. For the carbazole-(H 2 O) 1 complex, two bands with a spectral shift of 0.57 cm −1 were recorded under exposure to radiation with a spectral width of 0.08 cm −1 at the frequency of the purely electronic transition and some other electronic-vibrational transitions. This is caused by the tunnel effect. The intensities of the shifted low-frequency bands are threefold weaker than those of high-frequency bands due to different values of nuclear spin-statistical weights. In the carbazole-(H 2 O) 2 and carbazole-(H 2 O) 3 complexes, water molecules are combined into a chain by the hydrogen bond, and the two ends of the chain are hydrogen-bonded to the carbazole molecule. The principal axes I A and I B of the moments of inertia in carbazole-(H 2 O) 3 have different orientation compared to the other complexes considered, and this leads to an increase in the intensity of the Q -branch.

We have analyzed the fluorescence excitation spectra of carbazole complexes with a single molecule of methyl, deuterated methyl, ethyl, and propyl (1-propanol and 2-propanol) alcohols, cooled in a supersonic jet. We have determined the shifts in the fluorescence excitation spectra of the complexes relative to the frequency of the purely electronic transition of unbound carbazole. They occur as a result of formation of hydrogen bonds between the N-H group of the carbazole and the OH group of the alcohols. The frequencies of stretching vibrations of the hydrogen bonds with different alcohols vary within the range 150–157 cm−1, while the frequencies of the bending vibrations vary in the range 21–22.9 cm−1. From the shape of the rotational contours of the bands for the purely electronic and vibronic transitions of the complexes, we determined that they belonged to rotational conformers. We calculated the equilibrium configurations of the complexes in the ground state.

Rotational contours of bands of electron and vibronic transitions of the fluorescence excitation spectrum of jet-cooled carbazole complexes with one, two and three water molecules are studied. For the carbazole-(H2O)(1) complex two bands separated at 0.57 cm(-1) are registered at excitation of pure electron transition and other electron and vibronic transitions by radiation with a spectral width of 0.08 cm(-1). This is caused by the tunnel effect. The intensities of the shifted low-frequency bands are three times as weak as the high-frequency ones because of different nuclear spin-statistical weights. Water molecules in carbazole-(H2O)(2) and carbazole-(H2O)(3) complexes are combined into a chain by the hydrogen bond. Both ends of this chain are also hydrogen-bonded with a carbazole molecule. There is the interchange of the axes I-A and I-B of the principal moments of inertia in the carbazole-(H2O)(3) complex, as compared to the remaining considered complexes. This results in increasing the Q-branch intensity.