Solvent effects on the absorption spectrum of the perylene-SbCl<Subscript>5</Subscript> complex

The perylene-SbCl₅ complex is characterized by two absorption maxima, whose positions depend on the nature of the solvent. The maximum in the region of 19×10⁻³ cm⁻¹ corresponds to the perylene cationic form and depends on the medium polarity, while another, in the region of 14×10⁻³ cm⁻¹, corresponding to the perylene-SbCl₅ complex, is governed primarily by the ability of the solvent to the electrophilic solvation. However, the quantitative generalization of the data on the frequencies of absorption maxima is only possible using multiparameter equations that take into account various properties of the solvents.     

Diffractive lenses for high-power terahertz radiation beams

Techniques for manufacturing silicon binary (two-level) diffractive lenses and polypropylene kinoform diffractive lenses for the terahertz spectrum range are described. The elements are 1 and 0.8 mm thick, respectively. The silicon lens is manufactured in two versions: with no coating and with a parylene C (polyparaxylylene) antireflection coating. Characteristics of the diffractive optical elements are studied in the beam of a pulse-periodic free electron laser at a radiation wavelength of 141 μm and a repetition rate of 5.6MHz. The radiation resistance of the parylene coating, tested on the Novosibirsk free electron laser, was not impaired when the coating was exposed to an average power density of 4 kW cm^?2, the peak power in a 100-picosecond pulse being almost 8 MW cm^?2.     

Diffraction-free beams and their caustics

We discuss the feasibility of generating focal areas in different diffraction fields and prove that the term ‘diffraction-free’ beams is used to designate a spatially limited portion of the toroidal light wave. The light line, or axial caustic, is a result of interference of intersecting areas of this wave. It is shown that the ‘diffraction-free’ beams are generated by such optical elements whose phase transmission function includes linear terms with respect to the radial coordinate. A comparison of optical characteristics of caustics in the near- and far-diffraction fields is made. Synthesis of a new diffraction-modulated axicon that forms two focal areas of different types is reported. The results of experimental studies of its optical characteristics are discussed.     

Diffractive interferometer for visualization and measurement of optical heterogeneities

New optical arrangements of the two beam diffractive interferometer with the inverted wave fronts and the combined optical branches based on zone plates are proposed. The special software is designed. The restitution of an interference pattern is performed; the skeleton of fringes is selected; the graphic visualization of optical heterogeneity of a sample is built in the computer-aided processing of interferograms. Proposed DI enable visualizing the optical thickness heterogeneities in the transparent sample, measuring them with accuracy ～0.05λ and can be used for research and quality surveillance of laser crystals and other optical materials.     

Electromagnetic scattering by a homogeneous chiral obstacle in a chiral environment

Time-harmonic electromagnetic waves are scattered by a homogeneouschiral obstacle embedded in a chiral environment. The correspondingtransmission problem is reduced, via Bohren's decomposition,to an integral equation over the interface between the obstacleand the surrounding medium. This integral equation is shownto be uniquely solvable except for a discrete set of electromagneticparameters of the obstacle.