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971.
J. Links K. Hibberd M. Gould A. Foerster 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):309-312
A new model for correlated electrons is presented which is integrable in one-dimension. The symmetry algebra of the model
is the Lie superalgebra gl(2|1) which depends on a continuous free parameter. This symmetry algebra contains the pairing algebra as a subalgebra which is used to show that the model exhibits Off-Diagonal Long-Range Order in any number
of dimensions.
Received: 9 December 1997 / Revised: 12 February 1998 / Accepted: 17 March 1998 相似文献
972.
3 is reported. Using an external cavity diode laser, tunable from 795 to 825 nm, and a cw diode-pumped Nd:YAG ring laser at
1064 nm, we produced narrowband mid-ir laser light between 3.16 and 3.67 μm. This broad tuning range of 440 cm-1 can be critically phase-matched by changing the external crystal angle within a range of only 0.4°. Even for a fixed crystal
angle broadband phase-matching over 230 cm-1 was achieved. No realignment was required when tuning the laser over the whole wavelength range, which enabled the use of
a compact 36-m multipass cell as gas chamber. The conversion efficiency could be improved by almost a factor of 3 by applying
noncollinear instead of collinear phase-matching, resulting in 30 nW of idler power with good beam quality. Spectra of methane
were recorded in laboratory air, which demonstrate the rapid and continuous broad tunability at high sensitivity, enabling
sub-ppm detection. Finally, wavelength modulation spectroscopy at high resolution was applied as a promising tool for further
inproving the performance of this laser spectrometer.
Received: 16 March 1998/Revised version: 1 July 1998 相似文献
973.
Z.-C. Wang Z.-Y. Chen Y. Xu 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(2):185-190
A theoretical study is made of the steady-state populations of a three-level atom in a ladder configuration, driven by a superposition
of a monochromatic laser wave with a broad-band squeezed vacuum. The master equation for the system and the atomic Bloch equations
are derived. The steady-state populations are calculated numerically and shown graphically as functions of two-photon detuning
for various cases of the squeezed vacuum. It is shown that, the atomic populations depend strongly on the relative phase of
the driving field and the squeezed vacuum. When the phase matching condition is fulfilled, there will be a strong two-photon
resonant absorption from the squeezed vacuum, a characteristic different from absorption of photons from a classical field.
Received: 28 May 1997 / Revised and Accepted: 10 December 1997 相似文献
974.
C. Fort A. Bambini L. Cacciapuoti F.S. Cataliotti M. Prevedelli G.M. Tino M. Inguscio 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,3(2):113-118
We report on a theoretical and experimental investigation of 39K magneto-optical trapping. The small hyperfine splitting characterizing the upper level of the cooling transition affects
the cooling mechanism. In order to model the atom-laser interaction, the whole level structure of the D2 line has to be taken into account. Two different regimes have been recognized, one optimizing the loading of the trap, the
second minimizing the temperature of the atoms. We investigated these two regimes experimentally and found results in agreement
with the theoretical predictions.
Received: 6 March 1998 / Received in final form: 13 May 1998 / Accepted: 13 May 1998 相似文献
975.
R. Nassif Y. Boughaleb A. Hekkouri J.F. Gouyet M. Kolb 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,1(4):453-464
We examine the behaviour of the concentration profiles of particles with repulsive interactions diffusing on a host lattice.
At low temperature, the diffusion process is strongly influenced by the presence of ordered domains. We use mean field equations
and Monte-Carlo simulations to describe the various effects which influence the kinetic behaviour. An effective diffusion
coefficient is determined analytically and is compared with the simulations. Finite gradient effects on the ordered domains
and on the diffusion are discussed. The kinetics studied is relevant for superionic conductors, for intercalation and also
for the diffusion of particles adsorbed on a substrate.
Received: 26 June 1997 / Revised: 18 September 1997 / Accepted: 10 November 1997 相似文献
976.
M. Wilkinson B. Mehlig 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,1(4):397-398
We discuss the absorption of electromagnetic radiation in small conducting particles, in the case where the electron motion
is diffusive. We refine an earlier theory in which we calculated the absorption coefficient using an effective potential describing
the screened electric field. Our new theory incorporates the effects of non-locality in the electrical conductivity, and shows
how the two limiting behaviours of the effective potential at high and low frequencies can be derived from a unified theory.
Our results are in full agreement with our earlier calculation.
Received: 3 November 1997 / Accepted: 29 January 1998 相似文献
977.
AFM study of gold nanowire array electrodeposited within anodic aluminum oxide template 总被引:7,自引:0,他引:7
Uniform gold nanowires were synthesized by electrodepositing the gold under a very low ac frequency in the pores of an anodic
aluminum oxide (AAO) template. The surface of the Au/AAO composite is very even and appeared purplish red. Atomic force microscopy
observation indicates that the template membranes we obtained have hexagonally close-packed nanochannels. The gold nanowire
array is very orderly arranged after partially dissolving the aluminum oxide membrane. Gold nanowires were also characterized
by transmission electron microscopy and the phase structure of the Au/AAO composite was proved by X-ray diffraction.
Received: 19 April 2001 / Accepted: 28 April 2001 / Published online: 27 June 2001 相似文献
978.
This paper is concerned with the preparation and characterization of cerium-substituted yttrium iron garnets, which are known
to be oxides having a large Faraday rotation effect. Using the improved flux method we successfully grew bulk single crystals
of iron garnet doped with Ce3+ ions with maximum substitutions up to 0.349. Here we investigate different solution compositions for maximum Ce3+ substitution. The Faraday rotation and optical absorption spectra were measured in the near infrared region for different
Ce3+ ion substituted iron garnets. The specific Faraday rotation of Ce0.349Eu0.195Y2.456Fe5O12 was found to be 1430 deg/cm at a wavelength of 780 nm and –1280 deg/cm at 1150 nm. The Ce substitution prominently enhances
the Faraday rotation effect, and Yb3+ and Eu3+ ions substituted for Y3+ in the dodecahedral sites of YIG can increase the concentration of Ce3+ ions, depressing the formation of nonmagnetic Ce4+ ions by charge compensation.
Received: 24 January 2001 / Accepted: 2 March 2001 / Published online: 27 June 2001 相似文献
979.
Received: 15 August 1997/Accepted: 13 November 1997 相似文献
980.
S.-J. An W.I. Park G.-C. Yi S. Cho 《Applied Physics A: Materials Science & Processing》2002,74(4):509-512
High-quality ZnO thin films were grown on single-crystalline Al2O3(0001) and amorphous SiO2/Si(100) substrates at 400–640 °C using laser molecular beam epitaxy. For film growth, the third harmonics of a pulsed Nd:YAG
laser were illuminated on a ZnO target. The ZnO films were epitaxially grown on Al2O3(0001) with the narrow X-ray diffraction full width at half maximum (FWHM) of 0.04° and the films on SiO2/Si(100) exhibited a preferred c-axis orientation. Furthermore, the films exhibited excellent optical properties in photoluminescence
(PL) measurements with very sharp excitonic and weak deep-level emission peaks. At 15 K, PL FWHM values of the films grown
on Al2O3(0001) and SiO2/Si(100) were 3 and 18 meV, respectively.
Received: 8 May 2001 / Accepted: 18 September 2001 / Published online: 20 December 2001 相似文献