Influence of Substituent in Conjugated Chain of Molecules on Nanocomponents Composition of Polymethine Dye Films

Molecular layers of polymethine dye long conjugation chain on glass contain several types of molecular nanocomponents. The number and type of the components depend on the thickness of a layer. In thin layers, only monomolecular components (all-trans-stereoisomers and cis-isomers) are present. We studied a series of four dicarbocyanines and determined the steric structure of the nanocomponents of the layers. The layers of less than 1 monolayer thick contain up to 4 monomeric components. For monocis- and dicisisomers of the dyes studied, which are obtained from the all-trans form upon rotation of fragments of a molecule around different bonds in the conjugated chain, the steric models were constructed. It was shown that in the series of polymethine molecules differing in the substituents and their positions in the chain there is a correlation between the intensity of the absorption bands of the certain components and the steric hindrance of molecular isomers. The above correlation may be used for the determination of the steric structure of monomeric components of the layer. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3489

Theoretical consideration of pits recording and etching processes in chalcogenide vitreous semiconductors

We propose theoretical consideration and computer modeling of information pit recording and etching processes in chalcogenide vitreous semiconductors. We demonstrate how to record and develop information pits with the necessary shape and sizes in chalcogenide photoresists using gaussian laser beam and selective etching. It has been shown that phototransformed region cross-section could be almost trapezoidal or parabolic depending on the photoresist material optical absorption, recording beam power, exposure, etchant selectivity and etching time. After illumination, the spatial distribution of photo-transformed material fraction was calculated using the Kolmogorov-Awrami equation. Analyzing obtained results, we derived a rather simple approximate analytical expression for the dependence of the photo-transformed region width and depth on the recording gaussian beam power, radius and exposure time. Then the selective etching process was simulated numerically. The obtained results quantitatively describes the characteristics of pits recorded by the gaussian laser beam in thin layers of As40S60 chalcogenide semiconductor.Comment: 14 pages, 1 scheme, 9 figure

Negative refraction and the spectral filtering of terahertz radiation by a photonic crystal prism

We demonstrate how micromachined photonic crystals can be used to negatively refract terahertz frequency light. The photonic crystals, which are constructed from conventional dielectric materials, manipulate the incident beam via interaction with their photonic bands. Consequently, we show that different components of a broadband beam incident on the structure may be positively or negatively refracted, depending upon its frequency and that the structure can be used as an effective spectral filter of THz radiation

Terahertz spectroscopy of polyaromatic hydrocarbons

In this work we are beginning to determine the terahertz dielectric properties of various polyaromatic hydrocarbons. Terahertz spectroscopy of such organic compounds has seen rather less work undertaken in recent years than that carried out in some other areas

An 'electromagnetic wiggler' originating from refraction of waves at the side edge of a Bragg reflector

Calculations are reported which predict that light incident on the side edge of a Bragg reflector can show varied and unusual refraction behaviour, including a rapid transition from positive to negative refraction. Although under certain conditions negative refraction can occur, it is concluded that perfect lensing based on it is unlikely to be realised in practice. However, it is shown that light incident obliquely on the structure can be made to propagate normal to the interface after refraction while exhibiting lateral oscillations of its Poynting vector, an effect that could possibly find application in an 'electromagnetic wiggler'. It is also shown that negative group velocity rather than negative effective mass is required for the observation of the negative refraction, and in the case of low refractive index contrast, negative refraction occurs only when the size of the illumination spot exceeds a critical value, which is inversely proportional to the contrast of the refractive indices