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21.
The softening of the IR active 300 cm−1 phonon mode in Tl-2223 superconductor, aroundT
c has been explained by considering a sixth order polarization potential at the off-center oxygen ion site in the Tl-O plane,
and by using a nonlinear lattice dynamical theory. The present theory explains, more or less satisfactorily, the unusual temperature
dependence of oxygen ion vibration and frequency shifts at higher temperature. The existence of strong nonlinear electron-phonon
interaction atT
c has been emphasized. 相似文献
22.
23.
We have calculated the phonon and periodon dispersion relations in IV–VI semi-conducting bulk PbTe and SnTe and their superlattice
structure. The model used here is a one-dimensional lattice which includes harmonic interactions up to second neighbours as
well as on-site nonlinear electron-ion interactions at the anion site. We calculate the phonon and periodon dispersion relations
in bulk and PbTe-SnTe superlattice for the transverse optic and acoustic modes using the transfer matrix method. Our analysis
has predicted correct nature of the folding of acoustic and confinement of optical phonons at various frequency intervals
corresponding to pass and stop bands of the superlattices. 相似文献
24.
Hema Tresa Varghese C. Yohannan Panicker Daizy Philip Joydeep Chowdhury Manash Ghosh 《Journal of Raman spectroscopy : JRS》2007,38(3):323-331
IR, Raman and surface enhanced Raman scattering (SERS) spectra of 3,5‐dinitrosalicylic acid (DNSA) were recorded and analysed. The vibrational wavenumbers were computed by the ab initio method using RHF/6–21G* basis and they were found to be in good agreement with the experimental values. The effect of the concentration dependence on the SERS intensity of the molecule was studied. The molecular plane assumes a tilted orientation with respect to the silver surface. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
25.
Residual stress can adversely affect the mechanical, electronic, optical and magnetic properties of thin films. This work describes a simple stress measurement instrument based on the bending beam method together with a sensitive non-contact fibre optical displacement sensor. The fibre optical displacement sensor is interfaced to a computer and a Labview programme enables film stress to be determined from changes in the radius of curvature of the film-substrate system. The stress measurement instrument was tested for two different kinds of thin film, hard amorphous carbon nitride (CN) and soft copper (Cu) films on silicon substrates deposited by RF magnetron sputtering. Residual stress developed in 500 nm thick CN thin films deposited at substrate temperatures in the range 50-550 °C was examined and it was found that stress in CN films decreased from 0.83 to 0.44 GPa compressive with increase of substrate temperature. Residual stress was found to be tensile (121 MPa) for Cu films of thickness 1500 nm deposited at room temperature. 相似文献
26.
Effect of variation of dielectric constant on the magnetic field modulation of exciplex luminescence
The effect of variation of dielectric constant on the relative magnetic field effect in singlet luminescence has been studied
using a typical exciplex system at a saturating field. The study indicates strong specificity in the perturbation of the magnetic
field effect by alcoholic solvents. In contrast to alcohols where relative singlet magnetic field effect is of the order of
2% only, the magnetic field effect in non-alcoholic medium reaches as high as 9%. Moreover, dielectric constant variation
in alcohols yields curves which are distinctly different from those in non-alcoholic media. It turns out that this dependence
of magnetic field effect on dielectric constant is similar in all non-alcoholic solvent mixtures. An analytical study based
on Hong and Noolandi’s solution of Smoluchowski equation has been made. Derived expressions can interpret experimental curves
reasonably well. 相似文献
27.
We deduce the Lax pair for a new space-dependent KdV equation,
, via the technique of Painlevé analysis. From it, infinitely many conservation laws are deduced and the symplectic structure is obtained. 相似文献
28.
29.
Sabina Yasmin Z. Siti Rozaila Bijoy Sonker Barua Faruque-Uz-Zaman Chowdhury Md. Abdur Rashid 《辐射效应与固体损伤》2018,173(7-8):657-672
One sign of a vibrant Bangladeshi economy has been the move away from the use of more traditional housing materials towards a preference for modern constructional media. Glass, one such example, used both decoratively and in a structural context, offers various advantageous properties and facets including a protective feature against radiation that has not previously been considered. Current interest examines the dosimetric possibilities offered by the commercial glass as a secondary shield and also in retrospective ionising radiation exposure analysis. Four popular brands of window glass are investigated, all available within the local market (PHP-Bangladesh, Usmania-Bangladesh, Nasir-Bangladesh and Rider-China), all with the same thickness and colour, varying in terms of elemental weight fractions as evaluated by energy dispersive X-ray analysis. As potential attenuators of transmitted radiation thereby forming secondary barriers against radiation exposure from penetrating radiations, the four brands of glass have been studied using photon energies from 59 up to 1332 keV, a range of values representative of that potentially encountered in incidents. Use has been made of a well-shielded high-purity germanium γ-ray spectrometer and associated electronics, providing for evaluation of the characteristic barrier parameters of half-value layer, radiation protection efficiency and effective atomic number (Zeff). Of the four brands investigated, Rider provides superior secondary shielding performance. Concerning potential retrospective dosimetry the effective atomic number of the glass samples are comparable with that of the commercial thermoluminescence (TL) dosimeter TLD-200. At high doses, the TL yields are sufficient to provide for retrospective accident dosimetry. 相似文献
30.
Semiconductor nanoparticle and conducting polymer composite is an interesting class of materials for optoelectronic and photovoltaic device application. We have synthesized a composite of nanocrystalline PbS and conducting polymer MEH-PPV by chemical synthesis and studied the effect of swift heavy ion (SHI) irradiation on the composite material. The irradiation of the composite materials in thin film form is carried out with 120 MeV Si+9 ion beam at fluences from 5×1010 to 1013 ions/cm2. Fluence dependent optical and structural properties have been observed in optical absorption, PL and TEM studies. Reduction of nanoparticle size has been observed after irradiation. 相似文献