共查询到20条相似文献,搜索用时 15 毫秒
1.
It is generally believed that the ground state of the ferromagnetic Heisenberg-Dirac-Van Vleck Hamiltonians acting ons=1/2 spins of a lattice withN sites has the maximum possible value of the total spinS=N/2 and isN+1 times degenerate. We present a rigorous proof of this statement, independent of the lattice dimension and topology.
A member of the Doppler Institute of Mathematical Physics, Faculty of Nuclear Sciences and Physical Engineering, Czech Technical
University, Prague. 相似文献
2.
F. L. Bregolin M. Behar F. Dyment 《Applied Physics A: Materials Science & Processing》2009,95(2):501-505
The diffusion of nitrogen in α-Hf was studied in the temperature range of (823–1123) K using the ion implantation and nuclear resonance techniques. The
measurements show that the diffusion coefficients follow the Arrhenius behavior D(T)=D
0exp (−Q/RT) with D
0=(5.5±2.1)×10−7 m2/s and Q=(228±1) kJ/mol. A comparison of the present results with the previous one is done. 相似文献
3.
C. Hecht H. Kronemayer T. Dreier H. Wiggers C. Schulz 《Applied physics. B, Lasers and optics》2009,96(1):119-125
The iron-atom concentration distribution as well as the gas-phase temperature was measured via laser-induced fluorescence
(LIF) during iron-oxide nanoparticle synthesis in a low-pressure hydrogen/oxygen/argon flame reactor using ironpentacarbonyl
(Fe(CO)5) as precursor. Temperature measurements based on multi-line NO-LIF imaging are used to correct for temperature-dependent
ground-state populations. The concentration measurement is calibrated based on line-of-sight absorption measurements. The
influence of the precursor on the flame is observed at precursor concentrations larger than 70 ppm as the flame front moves
closer to the burner surface with increasing Fe(CO)5 concentration. 相似文献
4.
S. Engstler G. Raimann C. Angulo U. Greife C. Rolfs U. Schröder E. Somorjai B. Kirch K. Langanke 《Zeitschrift für Physik A Hadrons and Nuclei》1992,342(4):471-482
The fusion reactions6Li(p, )3He,6Li(d, )4He, and7Li(p, )4He have been studied over the c.m. energy rangeE=10 to 1450 keV. Each reaction involved the use of hydrogen projectiles and LiF solid targets as well as Li projectiles and hydrogen molecular gas targets. In all cases the effects of electron screening on the low-energy fusion cross sections (exponential enhancement) have been observed; the effects are somewhat stronger in the case of atomicp ord projectiles compared to the case of molecularH
2
orD
2
gas targets. If isotopic effects on electron screening are negligible, all three reactions should exhibit the same enhancements for each set of experimental techniques. The measurements confirmed this expectation to a large extent.Supported in part by the Landesamt Nordrhein-Westfalen (IVA5-10600387), the Deutsche Forschungsgemeinschaft (Ro429/ 18-2 and Ro429/21-1), and the Comision Interministerial de Ciencia y Tecnologia (AEN90-0932) 相似文献
5.
Stefan Haas Gunnar Schöpe Christoph Zahren Helmut Stiebig 《Applied Physics A: Materials Science & Processing》2008,92(4):755-759
A detailed analysis of the monolithical series connection of thin-film silicon modules with ZnO/Ag back contact is presented.
In this study, pulsed lasers with wavelengths of 1064 nm and 532 nm were used. The influence of various laser parameters like
laser power, pulse overlap, etc., on the different patterning steps is discussed. The focus of this study was on the back
contact patterning process. Here (i) the flake formation process during the ablation and (ii) the influence of a NIR-laser
source as an alternative approach to the green laser were investigated in detail. The latter would reduce system costs if
only one NIR-laser source could be used for all patterning steps. 相似文献
6.
H. M. Hoang U. Garuska D. Kielan A. Marcinkowski B. Zwieglinski 《Zeitschrift für Physik A Hadrons and Nuclei》1992,342(3):283-290
Cross sections for70,72,73,74Ge(n, p)70,72,73,74Ga,70Ge(n, 2n)69Ge,72Ge (n,)69Zn
m
and74Ge(n, )71Zn
m
reactions are measured in the energy range from 13.0 to 16.6 MeV by the activation method using Ge(Li) detector-ray spectroscopy and compared with predictions of the reaction model incorporating preequilibrium and equilibrium emission mechanisms to interpret the energy dependence of the isotopic effect occuring in the (n, p) reaction. The fitted single-particle state-density parametersg, determined here for the germaniums are discussed together with theg-values found previously for the Se, Zr and Pd isotopic chains. A validity of the consistency condition between the precompound and compound models, which relatesg to the experimental level-density parametera viaa=
2
g/6 is demonstrated. 相似文献
7.
8.
D. Nodop S. Linke F. Jansen J. Limpert A. Tünnermann L. Rindorf 《Applied physics. B, Lasers and optics》2008,92(4):509-512
We report for the first time, to the best of our knowledge, on the fabrication and characterization of CO2-laser written long-period gratings in a large-mode area photonic crystal fiber with a core diameter of 25 μm. The gratings
have low insertion losses (<1 dB) and high attenuation (>10 dB) at the resonant wavelengths, making them particularly interesting
for high power applications. 相似文献
9.
10.
J. Z. Hu Z. W. Yu X. B. Wang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,51(3):381-385
We analyze the problem of approximate quantum cloning when the
quantum state is between two latitudes on the Bloch’s sphere. We
present an analytical formula for the optimized 1-to-2 cloning. The
formula unifies the universal quantum cloning (UQCM) and the phase covariant quantum cloning. 相似文献
11.
Masato Ohmukai Nobutomo Uehara Tetsuya Yamasaki Yasuo Tsutsumi 《Czechoslovak Journal of Physics》2004,54(7):781-784
We have investigated the effects of chemical etching on Raman spectra of porous silicon. The as-anodized porous silicon consisted
mainly of crystalline silicon, as indicated by the Raman spectra. The background in the spectrum was strong, indicating that
the porous silicon surface was rough due to the presence of pores. When chemical etching was performed five times, the Raman
spectrum revealed the presence of spherically shaped nanocrystalline silicon whose diameter was around 3.5 nm. Further chemical
etching, however, extinguished the nanocrystallites, in addition to smoothing the surface morphology. 相似文献
12.
J. Cifre J. Bertomeu J. Puigdollers M. C. Polo J. Andreu A. Lloret 《Applied Physics A: Materials Science & Processing》1994,59(6):645-651
Silicon films were deposited at moderate substrate temperatures (280–500° C) from pure silane and a silane-hydrogen mixture (10% SiH4, 90% H2) in a hotwire CVD reactor. The morphology, structure and composition of the samples were studied with scanning electron microscopy, transmission electron microscopy, transmission electron diffraction, X-ray diffraction, Raman spectroscopy and secondary ion mass spectrometry. The sample deposited at 500° C with pure silane has an amorphous structure, whereas the samples obtained from silane diluted in hydrogen have a polycrystalline structure, even that grown at the lowest temperature (280° C). Polycrystalline samples have a columnar structure with 0.3–1 m crystallite sizes with preferential orientation in [220] direction. Deposition rates depend on the filament-substrate distance and range from 9.5 to 37 Å/s for the polycrystalline samples. The high quality of the polycrystalline samples obtained makes the hot-wire technique very promising. Moreover, it is expected to be easily scaled up for applications to large-area optoelectronic devices and to photovoltaic solar cells. 相似文献
13.
D. Lambrecht T. Blaich T. W. Elze H. Emling H. Freiesleben K. Grimm W. Henning R. Holzmann J. G. Keller H. Klingler J. V. Kratz R. Kulessa S. Lange Y. Leifels E. Lubkiewicz E. F. Moore W. Prokopowicz R. Schmidt C. Schütter H. Spies K. Stelzer J. Stroth E. Wajda W. Waluś M. Zinser E. Zude 《Zeitschrift für Physik A Hadrons and Nuclei》1994,350(2):115-120
We investigate the beam energy dependence of neutron and proton squeeze-out in collisions of197Au+197Au atE/A=400—800 MeV. The azimuthal anisotropy that describes the enhanced emission of mid-rapidity neutrons perpendicular to the reaction plane rises strongly with the transverse momentum of the neutrons. This dependence of the azimuthal anisotropy follows a universal curve — independent of beam energy — if the neutron momenta are measured in fractions of the projectile momentum per mass unit. Analogously, the kinetic energy spectra of mid-rapidity neutrons exhibit a universal behaviour as a function of the kinetic energy of the projectile.
The members of the FOPI-collaboration: J.P. Alard, Z. Basrak, N. Bastid, I.M. Belayev, M. Bini, R. Bock, A. Buta, R. aplar, C. Cerruti, N. Cindro, J.P. Coffin, M. Crouau, P. Dupieux, J. Erö, Z.G. Fan, P. Fintz, Z. Fodor, R. Freifelder, L. Fraysse, S. Frolov, A. Gobbi, Y. Grigorian, G. Guillaume, N. Herrmann, K.D. Hildenbrand, S. Hölbling, O. Houari, S.C. Jeong, M. Jorio, F. Jundt, J. Kecskemeti, P. Koncz, Y. Korchagin, R. Kotte, M. Krämer, C. Kuhn, I. Legrand, A. Lebedev, C. Maguire, V. Manko, T. Matulewicz, G. Mgebrishvili, J. Mösner, D. Moisa, G. Montarou, P. Morel, W. Neubert, A. Olmi, G. Pasquali, D. Pelte, M. Petrovici, G. Poggi, F. Rami, W. Reisdorf, A. Sadchikov, D. Schüll, Z. Seres, B. Sikora, V. Simion, S. Smolyankin, U. Sodan, N. Taccetti, K. Teh, R. Tezkratt, M. Trzaska, M.A. Vasiliev, P. Wagner, J.P. Wessels, T. Wienold, Z. Wilhelmi, D. Wohlfarth, A.V. Zhilin. 相似文献
14.
G. A. Lalazissis S. E. Massen C. P. Panos 《Zeitschrift für Physik A Hadrons and Nuclei》1994,348(4):257-261
The inlfuence of state dependent short range correlations on the occupation numbers of the single particle shell model orbits of the doubly closed shell nuclei16O and40Ca is examined. The study shows that the effect of the state dependence of the short range correlations is rather small. The total depletion of the nuclear Fermi sea changes slightly compared with the one calculated by considering state independent short range correlations. 相似文献
15.
Temperature dependence of photoconductivity and persistent photoconductivity of single ZnO nanowires 总被引:1,自引:0,他引:1
Zhi-Min Liao Yi Lu Jun Xu Jing-Min Zhang Da-Peng Yu 《Applied Physics A: Materials Science & Processing》2009,95(2):363-366
Photoelectrical properties of single ZnO nanowires have been investigated using photocurrent–voltage characteristics measurements
varying with excitation photon energy and temperature. It is found that persistent photoconductivity (PPC) exists, and the
PPC decreases with decreasing temperature. The temperature dependence of the PPC effect indicates that thermally activated
return of electrons from shallow traps is responsible for the PPC phenomenon. The photosensitivity is found to be linear with
the applied voltage, and it increases with decreasing temperature. A temperature dependence of photoconductivity gain was
introduced to explain the experimental results. 相似文献
16.
InSe:Ho single crystal was grown by Bridgman-Stockberger method. Electric field effects on the absorption measurements have
been investigated as a function of temperature in InSe:Ho single crystal. The absorption edge shifted towards longer wavelengths
and a decrease of intensity in absorption spectra occurred under an electric field of 7.5 kV/cm. Using absorption measurements,
steepness parameter and Urbach energy were calculated under electric field. Applied electric field caused an increase in the
Urbach energy. At 10 K and 320 K, the first exciton energies were calculated as 1.322 and 1.301 eV for zero voltage and 1.245
and 1.232 eV for applied electric field, respectively. 相似文献
17.
Alexander J. Silenko 《The European Physical Journal C - Particles and Fields》2008,57(3):595-599
The exact solution of the Corben–Schwinger equations is obtained for spin-1 particles without an anomalous magnetic moment
in a uniform magnetic field. The exact Hamiltonian in the Foldy–Wouthuysen representation is derived. The conservation of
projections of the polarization operator onto four directions is proved. The approximate conservation of projections of this
operator onto the horizontal axes of the cylindrical coordinate system is established. For spin-1 particles with the anomalous
magnetic moment, the Hamiltonian in the Foldy–Wouthuysen representation is deduced within first order terms in the Planck
constant. Dynamics of spin-1 particles with the anomalous magnetic moment and their spins in the strong uniform magnetic field
are calculated. 相似文献
18.
Angular distributions and excitation functions for the emission of a large number of proton, deuteron, triton, and-particle groups in7Li+16O reactions have been measured in the vicinity of the Coulomb barrier. Within the framework of the statistical reaction model, two approaches are presented that can reproduce the only weakly anisotropic shape of the angular distributions and the absolute cross section for those groups of ejectiles where contributions from direct reaction modes are small. When a standard Woods-Saxon potential deduced from elastic scattering is used, the entrance channel angular momentum distribution must be limited to values below critical angular momental
cr which are smaller than the grazing angular momental
gr if fusion is to be described. A global proximity potential with a parameter set that has been adjusted to reproduce the fusion reactions of a variety of p- and sd-shell nuclei yields very similar results when applied to7Li+16O. The proximity potential effectively introduces a similar angular-momentum limitation. This analysis proves the existence of a fusion cross section limitation and the importance of strong direct reaction modes (transfer and possibly inelastic processes) in7Li+16O reactions at energies close to and even below the Coulomb barrier. Another aspect of7Li+16O is addressed briefly. The resonance-like structure observed in the heavy-ion radiative capture reaction7Li(16O,
0+1)23Na atE
x
(23Na)=25.4 MeV is not observed in the particle decay channels investigated in the present work.The authors would like to acknowledge the help received from B. Bellenberg, B. Dechant, H. Hemmert, T. Krischak, E. Kuhlmann, H. Putsch, and C. Scholz during the experiments. 相似文献
19.
I discuss the temperature dependence of quarkonium correlators calculated in lattice QCD. I show that the dominant source
of the temperature dependence comes from the zero-mode contribution, while the temperature dependence associated with the
melting of bound states is quite small. I study the zero-mode contribution quantitatively for various quark masses and show
that it is well described by a quasi-particle model with temperature-dependent heavy quark mass. As a byproduct, an estimate
of the medium dependence of the heavy-quark mass is obtained. 相似文献
20.
S. A. Bass C. Hartnack H. Stöcker W. Greiner 《Zeitschrift für Physik A Hadrons and Nuclei》1995,352(2):171-174
We present a microscopic calculation of neutronsqueeze-out in relativistic heavy ion collisions at beam energies betweeen 400 and 1000 MeV/nucleon. After demonstrating the importance of the correct isospin treatment for the neutron to proton ratio, our main emphasis is put on the investigation of the properties of neutronsqueeze-out. Thesqueeze-out ratio increases monotonously with the transverse momentum of the neutrons. This ratio is independent of the incident beam energy if plotted versusp
t
/p
proj
. Most importantly, we observe a strong dependence on the nuclear equation of state and momentum dependent interaction.Supported by GSI, BMFT and DFG 相似文献