D. A. Sapozhnikov

Structure-sensitive changes in the terahertz absorption spectra of merocyanine dye derivatives

The low-frequency vibrational modes of the series of merocyanines (malononitrile derivative) have been investigated by pulsed terahertz spectroscopy. The terahertz absorption spectra are shown to contain both intermolecular and intramolecular vibrational modes in the range of 0.15–3.45 THz (5–115 cm−1). An unambiguous correlation is established between the purposeful modification of the molecular structure of merocyanine dyes and the change in their terahertz absorption spectra.

A terahertz spectroscopic study of chitosan-based bionanocomposites containing clay nanoparticles

Dielectric properties of bionanocomposites resulting from regulated self-organization of chitosan and nanoparticles of synthetic saponite clay have been investigated by terahertz pulsed spectroscopy. Spectral characteristics of the composites considered in correlation with their structural features, which have been characterized by atomic force microscopy and scanning electron microscopy, depend on the concentration ratio of the components. The study of the effect of temperature on terahertz absorption spectra has led to the conclusion that hydrogen bonding may be involved in the formation of the bionanocomposites.

Vibrational spectra of corticosteroid hormones in the terahertz range

The terahertz time-domain and Raman spectra of corticosteroid hormones in the region of low-frequency infrared vibrations have been measured. On the ground of quantum chemical calculations of the frequencies and normal modes the assignments of vibrational bands in the THz-spectra are performed.

Terahertz applications of the materials made from nanostructured alumina oxyhydroxide (NOA), its modifications and composites

The properties of new porous materials made from nanostructured alumina oxyhydroxides (NAO) were studied in THz range. The effects observed with the raw, annealed, and chemically modified NOA have revealed properties allowing using such materials for various terahertz devices, particularly for a low loss holey waveguides. We also discuss the results of THz-TDS detection of adsorbed molecular layers at the NAO surface.

Investigation of spectral features of progesterone, 17a-hydroxyprogesterone and cortisone in THz range

The THz and Raman spectra of progesterone, 17a-hydroxyprogesterone and cortisone in the region of low-frequency infrared vibrations have been measured. Several intensive bands have unusual temperature dependence. Vibration frequencies are calculated by density functional theory.

Bulk, structural and interfacing water in the nanostructured alumina hydroxide studied by THz-TDS spectroscopy

We report what is believed to be the first measurements of dielectric properties in the terahertz frequency range of different types of water molecules existing in the bulk, structural or interfacing forms in the nanostructured alumina oxyhydroxide (NAO). We show that the dielectric permittivity associated with these kinds of water molecules differ from that of liquid bulk water.

Transient terahertz absorption spectroscopy and suppression of the NLO response of merocyanine derivatives of malonodinitriles

Excitation and relaxation dynamics of low frequency vibrational modes have been studied in the series of merocyanines - derivatives of malonodinitrile using optical pump - terahertz probe spectroscopy. The transient absorption spectra of the merocyanine derivatives exhibit specific features that were analysed in the context of molecular and electronic structural changes. For the first time we can explain the suppression of the nonlinear optical (NLO) response due to the excitation of the vibrations in the THz frequency range.

Terahertz time-domain spectroscopy and spectrochronography of amino acids and polypeptides

We present the Raman spectra of sulfur-containing biomolecules and the spectra measured in far-infrared region with the use of terahertz (THz) time-domain spectroscopic technique. The spectral features in THz and Raman spectra are different among sulfur-containing di- and tetrapeptides in powder. We are discussing the possibility to observe and to assign the low-frequency THz and Raman lines to the disulfide bridges.

The role of two-photon absorption and source size for THz generation in ZnTe

When focusing laser beam to a nonlinear crystal ZnTe the efficiency of THz pulse generation may be considerably limited by a two-photon absorption and small dimensions of polarization source compared to THz wavelength. The role of these factors were experimentally and theoretically studied, direction diagrams were measured.