ISSN:1057-9257    

DOI:10.1002/(SICI)1099-0712(199609)6:5/6<217::AID-AMO303>3.0.CO;2-T

出版商:John Wiley&Sons Ltd.    

年代:1996

数据来源: WILEY

摘要:

AbstractA new principal mechanism underlying real‐time holographic grating recording in a thin cell filled with a nematic liquid crystal doped with a dye is proposed. In the experiment a laser light interference pattern is mapped in the form of a spatial modulation of index of refraction. This is achieved by respective modulation of an electric field in the vicinity of the nematic liquid crystal due to its bulk photoconductivity and subsequent space charge field formation. In the spatially modulated electric field the nematic director is locally reoriented to some degree, leading to the appearance of a phase Δπ grating due to the birefringent properties of a nematic. The externally applied electric field plays an important role in the whole process: it changes the initial planar alignment of liquid crystal molecules and enhances the photogeneration quantum yield. The role of electrical edge conditions in the cell is pointed out as they determine the field distribution in the liquid crystal, which is generally different from the space charge field distribution described for photorefractive materi

ISSN:1057-9257    

DOI:10.1002/(SICI)1099-0712(199609)6:5/6<219::AID-AMO249>3.0.CO;2-4

出版商:John Wiley&Sons Ltd.    

年代:1996

数据来源: WILEY

摘要:

AbstractRoom‐temperature absorption spectra in non‐polar and polar solvents as well as the results of structural analysis of carbamic acidN‐(1‐phenylthio‐methyl)‐2‐methyl‐propylt‐butyl ester (C16H25O2NS, 1a) and phthalimide‐N‐(1‐phenylthio‐methyl)‐propane (C18H17O2NS, 1b) are presented. The β‐amino sulphide 1a crystallises in the tetragonal system, space groupP41, witha= 10.380(1) Å,b= 10.380(1) Å,c= 16.390(1) Å,a=B=y= 90°, while the β‐amino sulphide 1b crystallises in the monoclinic system, space groupP21, witha= 7.958(1) Å,b= 13.333(1) Å,c= 7.340(1) Å, β = 93.08(3)°. The spectroscopic properties of these compounds were also evaluated using the approximate all‐valence‐electron method (GRINDOL) including configuration interaction (Cl) together with the Langevin dipole/Monte Carlo technique to represent the solvent effect. Molecular polarisabilities and hyperpolarisabilities (βvec) were ca

ISSN:1057-9257    

DOI:10.1002/(SICI)1099-0712(199609)6:5/6<225::AID-AMO270>3.0.CO;2-2

出版商:John Wiley&Sons Ltd.    

年代:1996

数据来源: WILEY

摘要:

AbstractMolecular first‐order hyperpolarisabilities β of (donor)2‐acceptor type molecules have been determined by electric field induced second‐harmonic generation (EFISHG) experiments at 1.06 μm. The hyperpolarisability values are enhanced in these two dimensional charge transfer molecules, compared with a reference linear model molecule. One of these molecules absorbs part of the second‐harmonic beam. We propose a determination method for β that takes into account this phenomenon. Crystals of the title molecules exhibit second harmonic generation by the p

ISSN:1057-9257    

DOI:10.1002/(SICI)1099-0712(199609)6:5/6<233::AID-AMO272>3.0.CO;2-1

出版商:John Wiley&Sons Ltd.    

年代:1996

数据来源: WILEY

摘要:

AbstractBy changing the chemical composition of phthalocyanine molecules, the electrical properties of the ensemble in the solid state can be influenced directly. This is shown for phthalocyaninatomanganese (PcMn) as compared with purely divalent central metals and for complexes in which the ligand system has been modified by either electron‐withdrawing heteroatoms such as N instead of CH leading to tetrapyridotetraazaporphyrinatozinc (TPyTAPZn) or substituents such as F instead of H leading to hexadecafluorophthalocyaninatozinc (F16PcZn). The accessibility of additional oxidation states of Mn or the stabilisation of frontier orbital states by the ligand leads to a lower ionisation potential and interactions with impurities or dopant molecules are changed. A change in the observed majority carrier (n‐type behaviour) is seen even under UHV conditions. Measurements of the thermoelectric power and electrical conductivity are presented of the pure films and after exposure to oxidising ambient. During film growth either island growth or a growth following the Stranski‐Krastanov mechanism was observed. The comparison of the temperature dependence of thermopower and electrical conductivity leads to a discussion of the type of majority carriers, their generation as well as their transportation. For the materials investigated in this study the band model fails to explain the observed properties and a localised transport mechanism has to be considered. A transport in localised states close to the Fermi edge is discussed for TPyTAPZn and F1

ISSN:1057-9257    

DOI:10.1002/(SICI)1099-0712(199609)6:5/6<239::AID-AMO274>3.0.CO;2-E

出版商:John Wiley&Sons Ltd.    

年代:1996

数据来源: WILEY

摘要:

AbstractPersistent spectral hole burning in chlorin‐doped PVB provides a new method to record highly resolved images of extended objects of sufficient luminance such as the sun. The spectral resolution per pixel is much higher than with other methods, with the additional advantage of recording all the information in a single exposure. The signal‐to‐noise ratio has been greatly improved, making it possible to visualise the rotation of the sun on the basis of the Doppler shift of only one solar line. Since no selection about areas of interest has to be made beforehand (except for the limitations of the material itself), the method provides a useful tool for astronomical applications. However, to make it suitable for a broader range of experiments, new materials with higher quantum yields and a possibly broader inhomogeneous bandwidth would be n

ISSN:1057-9257    

DOI:10.1002/(SICI)1099-0712(199609)6:5/6<245::AID-AMO258>3.0.CO;2-F

出版商:John Wiley&Sons Ltd.    

年代:1996

数据来源: WILEY

摘要:

AbstractThe static and frequency‐dependent first hyperpolarisabilities (β) of three phenoxidepyridinium derivatives and Reichardt's betaine (ET30) have been computed in the gas phase and in aqueous solvent. The sum‐over‐states formalism is used to calculate individual components of the β‐tensors. The solvent effect was included via the Langevin dipole/Monte Carlo (LD/MC) approach. The influence of molecular geometry on the β‐tensors of betaine was investig

ISSN:1057-9257    

DOI:10.1002/(SICI)1099-0712(199609)6:5/6<248::AID-AMO250>3.0.CO;2-U

出版商:John Wiley&Sons Ltd.    

年代:1996

数据来源: WILEY

摘要:

AbstractWe report on the wealth of IR spectra of single crystals of the C60complex with chloro(triphenylphosphine)gold grown from toluene solution. The spectra are strongly temperature‐dependent at about 200 K. The dependence of the spectral parameters is attributed to variations in the molecular dynamics of the C60molecules and changes in the interactions between the fullerene and donor/solvent molecules. Some general considerations on the origin of the IR spectral variation vs. temperature are also presente

ISSN:1057-9257    

DOI:10.1002/(SICI)1099-0712(199609)6:5/6<255::AID-AMO268>3.0.CO;2-D

出版商:John Wiley&Sons Ltd.    

年代:1996

数据来源: WILEY

摘要:

AbstractIn this work we show that with strong hydrogen bonds, including a ‘very strong’ hydrogen bond and/or strong hydrogen‐bonding networks, highly non‐linear optically active chromophores, merocyanine dyes and phenol derivatives, are assembled as salt or semi‐salt crystals, leading to improvement in crystallinity and interesting non‐linear optical properties. Our approach is discussed in connection with four co‐cryst

ISSN:1057-9257    

DOI:10.1002/(SICI)1099-0712(199609)6:5/6<261::AID-AMO279>3.0.CO;2-K

出版商:John Wiley&Sons Ltd.    

年代:1996

数据来源: WILEY

摘要:

AbstractThe flow of water through a system filled with anthracene crystals was examined. For other materials it is known that the flow causes a difference in the potential and the short‐circuit current. We found that this potential, which is the electrokinetic potential, can be described using a strictly determined space charge distribution of charge carriers near the anthracene crystals and a given model of the water flow between the crystals. The aim of this paper is to present the influence of the spatial charge carrier distribution near the crystal surface on the potential and the current. Considering the laminar flow of water, we can estimate the electrokinetic potential and the current which occur because of the movement of carriers. This movement is forced by the water flow. Achieved values of the potential and the current were about 1 V and 1 μA respectively. Theoretical calculations agree with our experimental resu

ISSN:1057-9257    

DOI:10.1002/(SICI)1099-0712(199609)6:5/6<267::AID-AMO255>3.0.CO;2-G

出版商:John Wiley&Sons Ltd.    

年代:1996

数据来源: WILEY