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981.
Biswas N Thomas S Kapoor S Mishra A Wategaonkar S Venkateswaran S Mukherjee T 《The journal of physical chemistry. A》2006,110(5):1805-1811
Resonance Raman (RR) and surface-enhanced resonance Raman scattering (SERRS) of 4'-(N,N'-dimethylaminostyryl)-4-propylpyridinium bromide (hemicyanine, HC dye) in acetonitrile solution and on a colloidal silver surface have been investigated. The structure of the dye in the ground (S0) and excited (S1) electronic states was optimized using density functional calculations along with the B3LYP and the configuration interaction with the singlet excitation (CIS) methods, respectively, using the 6-31G basis set. The vibrational frequencies of the molecule were computed at the optimized geometry and compared with the observed Raman bands. A complete normal-mode analysis has been carried out because it is essential for the accurate assignment of the vibrational spectra. From the observed enhancement along various in-plane and out-of-plane vibrations in the SERRS spectrum and from theoretical calculations, it has been inferred that the interaction with the silver surface occurs via the nitrogen lone pair of the pyridyl or the dimethylamino group of the molecule with a tilted orientation. The observed red-shifts in the SERRS spectrum along various vibrations indicate strong interaction (chemisorption) of the HC dye with the silver surface. This is also supported by the presence of a Ag-N stretching vibration at 241 cm(-1). The effect of the dye concentration on the orientation of the molecule is also discussed. 相似文献
982.
R. Biswal P. K. Agrawal G. K. Mishra S. V. Nakhe S. K. Dixit J. K. Mittal 《Pramana》2010,75(5):953-959
This paper presents the design and performance analysis of an indigenously developed 110 W average output power copper HyBrID
laser operating at 16 kHz pulse repetition rate. The laser active medium was confined within a fused silica tube of ∼6 cm
diameter and ∼200 cm active length. An in-house developed high-power (∼10 kW) solidstate pulser was used as the electrical
excitation source. A simple estimation of deposited electrical power, at the laser head, was carried out and based on it,
the laser tube efficiency was found to be 2.9% at 70 W and 2.2% at 110 W laser power levels. 相似文献
983.
The Schrödinger equation was solved for a generalized PT-symmetric quartic potential in two dimensions. It was found that, under a suitable ansatz for the wave function, the system possessed real and discrete energy eigenvalues. Analytic expressions for the energy eigenvalues and the eigenfunctions for the first four states were obtained. Some constraining relations among the wave function parameters rendered the problem quasi-solvable. 相似文献
984.
A. Mishra A. Kumar S. Sanyal V. Dexheimer S. Schramm 《The European Physical Journal A - Hadrons and Nuclei》2010,45(2):169-177
The modification of kaon and antikaon properties in the interior of (proto-)neutron stars is investigated using a chiral SU(3) model. The parameters of the model are fitted to nuclear-matter saturation properties, baryon octet vacuum masses, hyperon
optical potentials and low-energy kaon-nucleon scattering lengths. We study the kaon/antikaon medium modification and explore
the possibility of antikaon condensation in (proto-)neutron star matter at zero as well as finite temperature/entropy and
neutrino content. The effect of hyperons on kaon and antikaon optical potentials is also investigated at different stages
of the neutron star evolution. 相似文献
985.
F.G. Fuchs A.D. McMurry S. Mishra N.H. Risebro K. Waagan 《Journal of computational physics》2010,229(11):4033-4058
Wave propagation in idealized stellar atmospheres is modeled by the equations of ideal MHD, together with the gravity source term. The waves are modeled as small perturbations of isothermal steady states of the system. We consider a formulation of ideal MHD based on the Godunov–Powell form, with an embedded potential magnetic field appearing as a parameter. The equations are discretized by finite volume schemes based on approximate Riemann solvers of the HLL type and upwind discretizations of the Godunov–Powell source terms. Local hydrostatic reconstructions and suitable discretization of the gravity source term lead to a well-balanced scheme, i.e., a scheme which exactly preserves a discrete version of the relevant steady states. Higher order of accuracy is obtained by employing suitable minmod, ENO and WENO reconstructions, based on the equilibrium variables, to construct a well-balanced scheme. The resulting high order well-balanced schemes are validated on a suite of numerical experiments involving complex magnetic fields. The schemes are observed to be robust and resolve the complex physics well. 相似文献
986.
Rupali Mishra Raghvendra S. Yadav Avinash C. Pandey Sharda. S. Sanjay 《Journal of luminescence》2010,130(3):365-198
We report the formation of highly stable and luminescent ZnO@Cd(OH)2 core-shell nanoparticles by simple introduction of cadmium salt in the initial precursor solution, used to synthesize ZnO nanoparticles by sol-gel route. The cadmium to zinc salt concentration ratio has been also varied to control the growth of ZnO nanoparticles at the smaller particle size. Formation of ZnO@Cd(OH)2 core-shell nanostructure has been confirmed by X-ray diffraction (XRD), energy dispersive analysis of X-rays (EDAX) and X-ray photoelectron spectroscopy (XPS). UV-vis absorption spectroscopy exhibits blue-shift in absorption edge on increasing cadmium concentrations. The photoluminescence emission spectra showed the remarkably stable and enhanced visible (green) emission from suspended ZnO@Cd(OH)2 nanoparticles in comparison to bare ZnO nanoparticles. It is postulated that Cd(OH)2 layer at the surface of ZnO nanoparticles prevents the agglomeration of nanoparticles and efficiently assists the trapping of hole at the surface site, a first step necessary for visible emission. The Fourier transform infrared spectroscopy (FTIR) also supports our assumption about surface chemistry. 相似文献
987.
Anuj Soni M.S. Kulkarni D.R. Mishra S.K. Gupta D.N. Sharma 《Journal of luminescence》2010,130(7):1308-497
Single crystals of α-Al2O3 (10×10 mm2, 0.4 mm thick) were annealed in vacuum at about 1500 °C in the ambience of boron. The OA studies on these samples showed bands at 203, 232 and 258 nm signifying that such a treatment leads to the formation of F and F+ centers in significant concentrations, these bands, however, were not found in the Al2O3 crystals processed in the similar manner in the absence of boron. The Al2O3:B samples were irradiated to different absorbed doses of 90Sr/90Y β-source and the continuous wave OSL (CW-OSL) was recorded on the samples using 470 nm blue light stimulation. These samples have shown a linear TL and CW-OSL response in the dose range of 20 mGy to 15 Gy. The minimum detectable dose, corresponding to 3σ limit of the variation of the output of the unirradiated dosimeters, was found to be 100 μGy. Irradiated samples stored in dark at room temperature for a period of two months show negligible fading. The TL and OSL sensitivities of the samples were found to be strongly dependent on process temperature and time. The TL response is marked by the absence of low temperature peak (<100 °C), unlike the case of α-Al2O3:C, implying that the boron doping does not lead to formation of shallow traps. The Al2O3:B samples show faster photoionisation cross-section as compared to α-Al2O3:C. This approach of processing of single crystal Al2O3 in the boron ambience thus represents a potential way of introducing dosimetrically pertinent defects in Al2O3 single crystals. 相似文献
988.
Measurements of the local susceptibility and 3d spin relaxation rate for single Fe impurities embedded in a nanocrystalline Nb host indicates the emergence of a local moment on Fe at and below a critical size of 11?nm. Our ab?initio electronic structure calculations show that the moment formation occurs due to Stoner enhancement arising from a size dependent lattice expansion and a consequent shift in the Fermi level. We also show that a size-induced positive host spin polarization of the Nb-4d band electrons strongly influences the fluctuation rate of the Fe moment. 相似文献
989.
Green luminescence and degradation of Ce3+ doped CaS nanocrystalline phosphors were studied with a 2 keV, 10 μA electron beam in an O2 environment. The nanophosphors were synthesized by the co-precipitation method. The samples were characterized using X-ray diffraction, Transmission electron microscopy, Scanning electron microscopy/electron dispersive X-ray spectroscopy and Photoluminescence (PL) spectroscopy. Cubic CaS with an average particle size of 42 ± 2 nm was obtained. PL emission was observed at 507 nm and a shoulder at 560 nm with an excitation wavelength of 460 nm. Auger electron spectroscopy and Cathodoluminescence (CL) were used to monitor the changes in the surface composition of the CaS:Ce3+ nanocrystalline phosphors during electron bombardment in an O2 environment. The effect of different oxygen pressures ranging from 1 × 10−8 to 1 × 10−6 Torr on the CL intensity was also investigated. A CaSO4 layer was observed on the surface after the electron beam degradation. The CL intensity was found to decrease up to 30% of its original intensity at 1 × 10−6 Torr oxygen pressure after an electron dose of 50 C/cm2. The formation of oxygen defects during electron bombardment may also be responsible for the decrease in CL intensity. 相似文献
990.
K. Lang A. Bodek F. Borcherding N. Giokaris I. E. Stockdale P. Auchincloss R. Blair C. Haber S. Mishra E. Oltman M. Ruiz F. J. Sciulli M. Shaevitz W. H. Smith R. Zhu Y. K. Chu D. B. MacFarlane R. L. Messner D. B. Novikoff M. V. Purohit D. Garfinkle F. S. Merritt M. Oreglia P. Reutens R. Coleman H. E. Fisk Y. Fukushima O. Kerns B. Jin D. Levinthal T. Kondo W. Marsh P. A. Rapidis S. Segler R. Stefanski D. Theriot H. B. White D. Yovanovitch O. Fackler K. Jenkins 《Zeitschrift fur Physik C Particles and Fields》1987,33(4):483-503
Neutrino interactions with two muons in the final state have been studied using the Fermilab narrow band beam. A sample of 18v μ like sign dimuon events withP μ>9 GeV/c yields 6.6±4.8 events after backgroud subtraction and a prompt rate of (1.0±0.7)×10?4 per single muon event. The kinematics of these events are compared with those of the non-prompt sources. A total of 437v μ and 31 \(\bar v_\mu \) opposite sign dimuon events withP μ>4.3 GeV/c are used to measure the strange quark content of the nucleon: \(\kappa = {{2s} \mathord{\left/ {\vphantom {{2s} {\left( {\bar u + \bar d} \right) = 0.52_{ - 0.15}^{ + 0.17} \left( {or\eta _s \frac{{2s}}{{u + d}} = 0.075 \pm 0.019} \right) for 100< E_v< 230 GeV\left( {\left\langle {Q^2 } \right\rangle = {{23 GeV^2 } \mathord{\left/ {\vphantom {{23 GeV^2 } {c^2 }}} \right. \kern-0em} {c^2 }}} \right)}}} \right. \kern-0em} {\left( {\bar u + \bar d} \right) = 0.52_{ - 0.15}^{ + 0.17} \left( {or\eta _s \frac{{2s}}{{u + d}} = 0.075 \pm 0.019} \right) for 100< E_v< 230 GeV\left( {\left\langle {Q^2 } \right\rangle = {{23 GeV^2 } \mathord{\left/ {\vphantom {{23 GeV^2 } {c^2 }}} \right. \kern-0em} {c^2 }}} \right)}}\) using a charm semileptonic branching ratio of (10.9±1.4)% extracted from measurements ine + e ? collisions and neutrino emulsion data. 相似文献