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Oscillator Model (oscillator + model)
Selected AbstractsTemperature-tuned band gap energy and oscillator parameters of Tl2InGaSe4 semiconducting layered single crystalsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 3 2009N. M. Gasanly Abstract The optical properties of Tl2InGaSe4 layered single crystals have been studied through the transmission and reflection measurements in the wavelength range of 500-1100 nm. The analysis of room temperature absorption data revealed the presence of both optical indirect and direct transitions with band gap energies of 1.86 and 2.05 eV, respectively. Transmission measurements carried out in the temperature range of 10-300 K revealed that the rate of change of the indirect band gap with temperature is , = , 4.4 × 10 -4 eV/K. The absolute zero value of the band gap energy was obtained as Egi(0) = 1.95 eV. The dispersion of the refractive index is discussed in terms of the single oscillator model. The refractive index dispersion parameters: oscillator wavelength and strength were found to be 2.53 × 10,7 m and 9.64 × 1013 m,2, respectively. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Theoretical study of NMR chemical shift induced by H/D isotope effectINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 15 2010Kimikazu Sugimori Abstract The isotope effect induced by deuterium substituted species is observed in molecular properties, such as geometry, kinetics, and electronic state, of the molecules through nuclear-electron interaction. Theoretical considerations and experimental alignments have been studied by ab initio molecular orbital, density functional theory, and other empirical strategies. The Born-Oppenheimer approximation with nuclear vibrational wavefunction can treat isotope effect because nuclear mass effect account for the average distance of vibrational motion. In this study, we introduce Morse anharmonic oscillator model to calculate average internuclear distance of diatomic molecules having X-H bonding and X-D bonding. Morse parameters are determined by fitting to potential energy surface of molecular orbital and/or density functional calculations, and then the average distance are obtained as the expectation value of the analytical Morse vibrational wavefunction. Nuclear magnetic resonance shielding constants of the H/D isotopomer are calculated again on the average distance by using GIAO with B3LYP and CCSD calculation. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source] Quantum quadratic brownian oscillator model for absorption lineshapesISRAEL JOURNAL OF CHEMISTRY, Issue 2-3 2002Valeri Barsegov The absorption lineshape of a two-level chromophore coupled quadratically to a collective Gaussian solvation coordinate with an arbitrary Brownian oscillator spectral density is calculated exactly using a path-integral representation of the dipole correlation function in Liouville space. [source] Analysis of Infrared Reflection Spectra of (Mg1,xZnx)Al2O4 Microwave Dielectric CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2008Chang Wei Zheng Infrared reflection spectra of (Mg1,xZnx)Al2O4 ceramics were analyzed by Kramers,Kroning analysis and classical oscillator model simulation. The dielectric properties were extrapolated down to the microwave range using the classical oscillator model for fitting the dielectric function. According to structure analysis, the losses originating from bend vibration and stretch vibration of the bond between A-site cation and oxygen anion dominated the whole dielectric losses of the spinel ceramics. The coexistence of Mg and Zn deteriorated the intrinsic dielectric properties due to the bond asymmetry thus introduced. The calculated Qf (,105 GHz) was much higher than the measured ones (,104 GHz), suggesting that the extrinsic loss was significant. Therefore, the microwave dielectric properties of MgAl2O4 and ZnAl2O4 could be improved much by microstructure modification, and the little superiority in their solution compared with the end-members was due to microstructure improvement. [source] Low-temperature single crystal reflection spectra of forsteriteMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006H. Suto ABSTRACT The infrared reflectivities of crystalline forsterite (Mg2SiO4) were measured for the temperature range 295,50 K for each crystal axis, between wavenumber 5000 and 100 cm,1. The reflection spectra show clear dependence of temperature; most of the bands become more intense, sharper and their peak positions shift to higher wavenumber with decreasing temperature. Reflection spectra were fitted with dispersion formula of damped oscillator model of the dielectric constants and the oscillator parameters in the model were derived. The absorption spectra of forsterite particle are calculated with the derived dielectric constants to show that the forsterite features are good thermal indicator for cold temperature range below 295 K. [source] Electrical conductivity and optical properties of poly(3-thiophene boronic acid) organic semiconductorPOLYMER ENGINEERING & SCIENCE, Issue 4 2009Fahrettin Yakuphanoglu Electrical conductivity and optical properties of the poly(3-thiophene boronic acid) have been investigated. The room temperature electrical conductivity and activation energy of the poly(3-thiophene boronic acid) were 2.0 × 10,9 S/cm and 0.17 eV, respectively. In the semiconductor region of the polymer, the charge transport mechanism is taking place by the hopping process in the localized states. The direct optical band gap value of the poly(3-thiophene boronic acid) was found to be 1.92 eV via optical absorption method. The width of localized states for the polymer was determined to be 0.36 eV. The refractive index dispersion curve of the polymer obeys the single oscillator model. The refractive index dispersion parameter Eo/So for the poly(3-thiophene boronic acid) was determined to be 9.82 × 1012 eV m2. The optical dielectric constants of the polymer were determined. The real part of the dielectric constant of the polymer is higher than that of imaginary part of the dielectric constant. The imaginary part shows a peak corresponding to the absorption edge. It is evaluated that the electrical and optical results of the poly(3-thiophene boronic acid) indicate that it is an organic semiconductor with electrical and optical parameters. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] Scanning Force Microscopy Based Rapid Force Curve Acquisition on Supported Lipid Bilayers: Experiments and Simulations Using Pulsed Force ModeCHEMPHYSCHEM, Issue 7 2004Stephanie Krüger Dr. Abstract In situ pulsed force mode scanning force microscopy (PFM,SFM) images of phase separated solid-supported lipid bilayers are discussed with the help of computer simulations. Simultaneous imaging of material properties and topography in a liquid environment by means of PFM,SFM is severely hampered by hydrodynamic damping of the cantilever. Stiffness and adhesion images of solid-supported membranes consisting of cholesterol, sphingomyelin, and 1,2-dioleyl-phosphatidylcholine obtained in aqueous solution exhibit contrast inversion of adhesion and stiffness images depending on parameters such as driving frequency, amplitude, and trigger setting. Simulations using a simple harmonic oscillator model explain experimental findings and give a deeper insight into the way PFM,SFM experiments have to be performed in order to obtain interpretable results and hence pave the way for reliable material contrast imaging at high speed. [source] Theoretical CD spectrum calculations of the crown-ether aralkyl-ammonium salt complex,CHIRALITY, Issue 5 2002Armand Lázár Abstract Rotatory strengths of the ,-(1-naphtyl)-ethylammonium perchlorate (NEA)-phenazino-18-crown-6 ether molecular complex is determined theoretically by the coupled oscillator model and using ab initio random phase approximation (RPA) to describe local excitations on the chromophores. The computational results are compared to the experimental circular dichroism (CD) spectrum published previously. The good qualitative agreement between calculated and measured optical rotatory strengths allows one to assign the CD bands of the complex in a unique manner. Chirality 14:377,385, 2002. © 2002 Wiley-Liss, Inc. [source] | ||||||||||||||||