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71.
Faisal A.A. El-Orany 《Optics Communications》2006,263(2):235-238
We prove that the revival-collapse phenomenon occurring in the atomic inversion of the two-photon Jaynes-Cummings model, when the mode is initially prepared in the coherent state and the atom is in the excited state, can be obtained from the evolution of the quadrature squeezing of the four-photon Jaynes-Cummings model. 相似文献
72.
Jaw-Luen Tang Chen-Wei Chen Jiunn-Yuan Lin Chia-Chen Hsu Tzer-Hsiang Huang 《Optics Communications》2006,266(2):669-675
Transient optical Kerr effect of liquids C2H4Cl2 and C2H4Br2 is investigated, for the first time to our knowledge, with a femtosecond (fs) probe laser delayed with respect to a coherent fs pump laser. Coherent coupling and electronic Kerr signals are observed around zero delay when pump and probe overlap. Persisting after the pump-probe overlap are Kerr signals arising from the torsional and other intramolecular vibrations of the trans and gauche conformations; Kerr signals arising from the intermolecular motion are also observed. Vibrational quantum interference is only observed in liquid C2H4Br2 and the related beats data are fitted with the torsional vibrations, 91 cm−1 (gauche) and 132 cm−1 (trans), and the CCBr angle-bending vibrations, 231 cm−1 (gauche) and 190 cm−1 (trans), with dephasing times, 0.45 ps, 0.45 ps, 2 ps, and 1.5 ps, respectively. These vibrational frequencies agree with those obtained in the frequency-domain. That no vibrational mode is observed for C2H4Cl2 might be attributed to ineffective Raman-pumping. Kerr signals observed after the pump-probe overlap are Fourier transformed to give the spectra of the intermolecular motion and the vibrational spectrum, which agrees with the one observed in the infrared absorption and/or Raman scattering heretofore. 相似文献
73.
Shao-Rui Sun 《Solid State Communications》2006,138(9):476-479
The DOS (density of states) and the optical properties of HgS under high pressure are studied with the first-principle computations. The change of the imaginary part, ε2(ω), of the dielectric function shows that HgS tends to metallization with increasing pressure, and this well agrees with the band gap calculations and the conductivities measurement results in the previous work. Under the pressures below 15 GPa, ε2(ω) is relatively anisotropic and tends to be more anisotropic with increasing pressure; while under the pressures above 15 GPa, the anisotropy decreases and finally becomes almost absolutely isotropic after the phase transition. The behavior of ε2(ω) is strongly related to the structure change in the cinnabar to rocksalt phase transition process under high pressure. 相似文献
74.
The elastic constants and thermodynamic properties of Li2O for high temperatures and pressures are calculated by the ab initio unrestricted Hartree-Fock (HF) linear combination of atomic orbital (LCAO) periodic approach. The lattice constant, elastic constants, Debye temperature, and thermal expansion coefficient obtained are in good agreement with the available experimental data and other theoretical results. It is found that at zero pressure the elastic constants C11, C12 and C44, bulk modulus B and Debye temperature ΘD decrease monotonically over the wide range of temperatures from 0 to 1100 K. When the temperature , C12 approaches zero, consistently with the transition temperature 1200 K. However, with increasing pressure, they all increase monotonically and the anisotropy will weaken. 相似文献
75.
A new BEDT-TTF-based salt with an organic free radical TEMPO has been prepared. The salt consists of alternate layers of conducting and magnetic sheets, between which are short S(BEDT-TTF) …O(TEMPO) contacts. The magnetic susceptibility is well modelled by the combination of a 2D Heisenberg and a Curie-Weiss model with and . 相似文献
76.
G. Spavieri V. Guerra R. De Abreu G. T. Gillies 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(3):457-463
Propagation of Aharonov-Bohm matter waves and light waves in moving media is
characterized by the interaction electromagnetic momentum. Thus, recent
models of light propagation in moving rarefied media justify and call for an optical experiment of the Mascart-Jamin type,
capable of testing the
modern interpretations of ether drift experiments. 相似文献
77.
The Gibbs-Thomson effect modifies the pressure and temperature at which clathrates occur, hence altering the depth at which they occur in the seabed. Nuclear magnetic resonance (NMR) measurements as a function of temperature are being conducted for water/ice/hydrate systems in a range of pore geometries, including templated SBA-15 silicas, controlled pore glasses and sol-gel silicas. Rotator-phase plastic ice is shown to be present in confined geometry, and bulk tetrahydrofuran hydrate is also shown to probably have a rotator phase. A novel NMR cryoporometry protocol, which probes both melting and freezing events while avoiding the usual problem of supercooling for the freezing event, has been developed. This enables a detailed probing of the system for a given pore size and geometry and the exploration of differences between hydrate formation and dissociation processes inside pores. These process differences have an important effect on the environment, as they impact on the ability of a marine hydrate system to re-form once warmed above a critical temperature. Ab initio quantum-mechanical molecular dynamics calculations are also being employed to probe the dynamics of liquids in pores at nanometric dimensions. 相似文献
78.
In this article, we present studies on therahertz (THz) wave generation and frequency up-conversion in a periodically poled lithium niobate (PPLN) crystal. A frequency at 1.37 THz was generated as femtosecond pump pulses passed through a PPLN crystal with grating periods of 30 μm. The pump-induced THz wave interacts with the probe wave in the crystal by frequency mixing. The frequency up-converted THz wave is easily detected by a normal photodiode. A new scheme for generation and detection of THz wave in one non-linear crystal was proposed. 相似文献
79.
The use of activated carbon obtained from Euphorbia rigida for the removal of a basic textile dye, which is methylene blue, from aqueous solutions at various contact times, pHs and temperatures was investigated. The plant material was chemically modified with H2SO4. The surface area of chemically modified activated carbon was 741.2 m2 g−1. The surface characterization of both plant- and activated carbon was undertaken using FTIR spectroscopic technique. The adsorption process attains equilibrium within 60 min. The experimental data indicated that the adsorption isotherms are well described by the Langmuir equilibrium isotherm equation and the calculated adsorption capacity of activated carbon was 114.45 mg g−1 at 40° C. The adsorption kinetics of methylene blue obeys the pseudo-second-order kinetic model and also followed by the intraparticle diffusion model up to 60 min. The thermodynamic parameters such as ΔG°, ΔH° and ΔS° were calculated to estimate the nature of adsorption. The activation energy of the system was calculated as 55.51 kJ mol−1. According to these results, prepared activated carbon could be used as a low-cost adsorbent to compare with the commercial activated carbon for the removal textile dyes from textile wastewater processes. 相似文献
80.
Structural characterisation of such bio-objects as fibrinogen solution, yeast cells, wheat seeds and bone tissues has been done using two versions of cryoporometry based on the integral Gibbs-Thomson (IGT) equation for freezing point depression of pore liquids and the measurements by 1H NMR spectroscopy (180-200 < T < 273 K) and the thermally stimulated depolarisation current (TSDC) method (90 < T < 273 K) of structured water. The IGT equation was solved using a self-consisting regularization procedure including the maximum entropy principle applied to the distribution function of pore size (PSD). Both methods give clear pictures of changes in the structural characteristics caused, e.g., by hydration and swelling of wheat seeds and yeast cells, coagulation and interaction of fibrinogen with solid nanoparticles in the aqueous media, and the human bone tissue disease. 相似文献