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Optical Behaviour (optical + behaviour)

Distribution by Scientific Domains

Physics and Astronomy	50%

Selected Abstracts

Comments on papers reporting IR-spectra and other data of alleged L-alanine alaninium nitrate and L-alanine sodium nitrate crystals

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 7 2009
M. Fleck
Abstract We argue that the IR- and Raman-spectra of "L-alanine alaninium nitrate" given in "Investigation on the growth, optical behaviour and factor group of an NLO crystal: L-Alanine Alaninium nitrate" by Aravindan et al., Cryst. Res. Technol. 42, 1097 (2007), actually concern L-Alanine. Correspondingly, the data presented in "A comparative study on the growth and characterization of nonlinear optical amino acid crystals: L-Alanine (LA) and L-alanine alaninium nitrate (LAAN)" by Aravindan et al., Spectrochim. Acta A 71, 297 (2008), seems to be erroneous, as is "Synthesis, Growth, and Characterization of a New Semiorganic Nonlinear Optical Crystal: L-Alanine Sodium Nitrate (LASN)", Sethuraman, et al., Cryst. Growth Des. 8, 1863 (2008). In these papers properties and data were reported for L-Alanine compounds that actually are L-Alanine crystals and, in addition, unit cell parameters were given that seem to have been copied from other papers. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Studies on the structural, thermal and optical behaviour of solution grown organic NLO material: 8-hydroxyquinoline

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 2 2007
N. Vijayan
Abstract Single crystal of 8-hydroxyquinoline (8HQ) having chemical formula C9H7NO, an organic nonlinear optical (NLO) material has been successfully grown by slow evaporation solution growth technique at room temperature. The crystal system has been confirmed from the powder X-ray diffraction (PXRD) analysis. The crystalline perfection was evaluated by high resolution X-ray diffractometry (HRXRD). From this analysis we found that the quality of the crystal is quite good. However, a very low angle (tilt angle 14 arc sec) boundary was observed which might be due to entrapping of solvent molecules in the crystal during growth. Its optical behavior has been examined by UV-Vis. analysis, which shows the absence of absorbance between the wavelengths ranging from 400 to 1200 nm. From the thermal analysis it was observed that the material exhibits single sharp weight loss starting at 113°C without any degradation. The laser damage threshold was measured at single shot mode and the SHG behavior has been tested using Nd:YAG laser as a source. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Synthesis, Characterisation and Nonlinear Optical Properties of Two-Dimensional Octupolar Systems Based on Phthalocyanine Compounds

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 18 2005
Maurizio Quintiliani
Abstract Four phthalocyanine-based compounds with pseudo D3h symmetry have been synthesised and fully characterised. Palladium cross-coupling methodologies were employed in order to synthesise 1,3,5-tris[(phthalocyaninyl)ethenyl]benzene (Heck) and 1,3,5-tris[(phthalocyaninyl)ethynyl]benzene (Sonogashira) derivatives. Knoevenagel condensation conditions were then applied to the synthesis of 1,3,5-tris[cyano(phthalocyaninyl)ethenyl]benzene and 2,4,6-tris[(phthalocyaninyl)ethenyl]-1,3,5-triazine. Preliminary second-order nonlinear optical studies, by hyper-Rayleigh scattering measurements, revealed that the compounds containing ethenyl linkers induce a strong octupolar effect while the ethynyl-containing compound does not show any octupolar enhancement. The introduction of a triazine central core does not modify significantly the nonlinear optical behaviour of the compound. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

XMM,Newton observations of UW CrB: detection of X-ray bursts and evidence for accretion disc evolution

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2005
Pasi Hakala
ABSTRACT UW CrB (MS 1603+2600) is a peculiar short-period X-ray binary that exhibits extraordinary optical behaviour. The shape of the optical light curve of the system changes drastically from night to night, without any changes in overall brightness. Here we report X-ray observations of UW CrB obtained with XMM,Newton. We find evidence for several X-ray bursts, confirming a neutron star primary. This considerably strengthens the case that UW CrB is an accretion disc corona system located at a distance of at least 5,7 kpc (3,5 kpc above the Galactic plane). The X-ray and Optical Monitor (ultraviolet,optical) light curves show remarkable shape variation from one observing run to another, which we suggest are due to large-scale variations in the accretion disc shape resulting from a warp that periodically obscures the optical and soft X-ray emission. This is also supported by the changes in phase-resolved X-ray spectra. [source]

Stress,optical behaviour of polyester networks

POLYMER INTERNATIONAL, Issue 3 2002
Evaristo Riande
Abstract Thermoelastic networks were prepared by end-linking hydroxyl terminated chains of poly(neopentylglycol hexafluoroglutarate) (PNGHFG) and poly(diethylene glycol terephthalate) (PDET) using, respectively, tri(p -isocyanate-phenyl)-thiophosphate and 2,4-bis(p -isocyanate benzyl)- p -phenylisocyanate as crosslinking agents. The plots of birefringence versus stress for PNGHFG and PDET networks exhibit negative deviations from linearity at elongation ratios greater than 1.9 and 5, respectively. The values of the optical configuration parameter ,a for the former and latter networks are 2.98,Å3 at 5,°C and 20.80,Å3 at 30,°C, respectively. Theoretical calculations carried out using the conformational energies obtained from the critical analysis of the mean-square dipole moments of diethyl hexafluoroglutarate and poly(neopentylglycol hexafluoroglutarate) give the value of 2.24,Å3 at 5,°C for this parameter, in fair agreement with the experimental result. Similar calculations carried out on PDET networks give ,a,,=,3.74,Å3 at 30,°C, a value significantly lower than the experimental result. The cause of the strong discrepancy between the theoretical and experimental results observed for the optical configuration parameter of PDET is discussed. © 2002 Society of Chemical Industry [source]

TCOs for nip thin film silicon solar cells

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 3 2009
T. Söderström
Abstract Substrate configuration allows for the deposition of thin film silicon (Si) solar cells on non-transparent substrates such as plastic sheets or metallic foils. In this work, we develop processes compatible with low Tg plastics. The amorphous Si (a-Si:H) and microcrystalline Si (µc-Si:H) films are deposited by plasma enhanced chemical vapour deposition, at very high excitation frequencies (VHF-PECVD). We investigate the optical behaviour of single and triple junction devices prepared with different back and front contacts. The back contact consists either of a 2D periodic grid with moderate slope, or of low pressure CVD (LP-CVD) ZnO with random pyramids of various sizes. The front contacts are either a 70,nm thick, nominally flat ITO or a rough 2,µm thick LP-CVD ZnO. We observe that, for a-Si:H, the cell performance depends critically on the combination of thin flat or thick rough front TCOs and the back contact. Indeed, for a-Si:H, a thick LP-CVD ZnO front contact provides more light trapping on the 2D periodic substrate. Then, we investigate the influence of the thick and thin TCOs in conjunction with thick absorbers (µc-Si:H). Because of the different nature of the optical systems (thick against thin absorber layer), the antireflection effect of ITO becomes more effective and the structure with the flat TCO provides as much light trapping as the rough LP-CVD ZnO. Finally, the conformality of the layers is investigated and guidelines are given to understand the effectiveness of the light trapping in devices deposited on periodic gratings. Copyright © 2008 John Wiley & Sons, Ltd. [source]