共查询到19条相似文献,搜索用时 140 毫秒
1.
刘烨 《原子与分子物理学报》2012,29(6)
本文数值计算了脉宽为半个光学周期的超短脉冲在不同载波包络相位下的谐波波谱,通过比较谐波波谱截止频率与电子通过主要路径可获得的最大动能的差异,研究了超短脉冲谐波辐射过程中的量子路径。结果显示,超短脉冲谐波辐射过程中电子获得动能的量子路径偏离主要量子路径,而且该偏离效应受载波包络相位的影响。 相似文献
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采用Lewenstein模型计算了两个不同脉宽的超短脉冲高次谐波截止频率与包络载波相位的关系, 结果显示,其截止频率随载波包络相位的增加先减小后增加。随着脉冲宽度的减小,高次谐波截止频率变化的幅度增加。我们按准经典的三步模型解释所得结果,并讨论了量子辐射效应。 相似文献
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通过数值求解一维含时薛定谔方程, 本文研究了具有特定波长的双色激光脉冲与氦原子相互作用产生的高次谐波和阿秒脉冲, 这里双色激光脉冲由5 fs较低强度基频钛宝石主脉冲与另一束较高强度的1330 nm 红外附加脉冲构成. 研究发现, 若两束脉冲之间的相对相位选择合适, 可以获得宽带连续辐射的高次谐波谱, 叠加该连续辐射谱可获得脉宽为38 as的孤立短脉冲. 进一步研究发现, 不同于以往孤立阿秒脉冲研究中选出长、短量子路径之一作为辐射源, 这里单阿秒脉冲来源于长、短两个量子路径的贡献, 只是这两个量子路径在很宽的谐波次数变化范围内辐射时刻比较集中.
关键词:
双色激光脉冲
阿秒脉冲
量子路径 相似文献
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研究了超短激光脉冲驱动的Thomson散射的辐射空间分布. 发现辐射的空间分布对称性显著地依赖于超短脉冲的载波相位η0,在η0=0,π时,辐射的空间分布呈现出二重或一重对称性;而在其他载波相位时,这些空间分布对称性遭到破坏. 辐射光的准直性也依赖于驱动脉冲的载波相位,在η0=±π/2时辐射光的准直性最好. 这些结果表明可以通过改变驱动激光脉冲的载波相位来控制辐射光的空间分布,也可以利用辐射空间分布对相位的依赖特性来测量超短激光脉冲的载波相位.
关键词:
Thomson散射
空间分布
载波相位 相似文献
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利用光参量放大过程输出的闲置光载波-包络相位(CEP)被动稳定的特点,搭建了三级光参量放大(OPA)系统,获得了CEP稳定的近红外高能量超短激光脉冲(1.4 mJ/40 fs/1 kHz @ 1.8 μm),其CEP抖动为516 mrad(rms).经空心光纤展宽光谱和块体材料补偿色散,激光脉宽最终可被压缩至小于两个光学周期(<12 fs),脉冲能量达到0.54 mJ.该系统为单个阿秒脉冲的产生和其他高次谐波实验提供了优质的光源.
关键词:
光参量放大
周期量级近红外激光脉冲
载波-包络相位稳定 相似文献
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F. Sh. Aidaev 《Journal of Applied Spectroscopy》2002,69(1):145-147
The quantum yield of the electroluminescence of EuGa2S4:Nd single crystals for the dependence of the mean free path of the electron on its kinetic energy and the kinetic energy square are calculated, as well as the impact excitation cross section of Nd3+ in the single crystals indicated. The mechanism of electron scattering is considered. 相似文献
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S. V. Shevkunov 《Journal of Experimental and Theoretical Physics》2013,117(4):699-717
The fundamental laws in the behavior of electrons in model quantum dots that are caused by exchange and strong Coulomb correlations are studied. The ab initio path integral method is used to numerically simulate systems of two, three, four, and six interacting identical electrons confined in a three-dimensional spherical potential well with a parabolic confining potential against the background of thermal fluctuations. The temperature dependences of spin and collective spin magnetic susceptibility are calculated for model quantum dots of various spatial sizes. A basically exact procedure is proposed for taking into account the permutation symmetry and the spin state of electrons, which makes it possible to perform numerical calculations using modern computer facilities. The conditions of applicability of a virial energy estimator and its optimum form in exchange systems are determined. A correlation estimator of kinetic energy, which is an alternative to a basic estimator, is suggested. A fundamental relation between the kinetic energy of a quantum particle and the character of its virtual diffusion in imaginary time is demonstrated. The process of natural “pairing” of electron spins during the compression of a quantum dot and cooling of a system is numerically reproduced in terms of path integrals. The temperature dependences of the spin magnetic susceptibility of electron pairs with a characteristic maximum caused by spin pairing are obtained. 相似文献
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The identification of kinetic pathways is a central issue in understanding the nature of flexible binding. A new approach is proposed here to study the dynamics of this binding-folding process through the establishment of a path integral framework on the underlying energy landscape. The dominant kinetic paths of binding and folding can be determined and quantified. In this case, the corresponding kinetic paths of binding are shown to be intimately correlated with those of folding and the dynamics becomes quite cooperative. The kinetic time can be obtained through the contributions from the dominant paths and has a U-shape dependence on temperature. 相似文献
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S. V. Shevkunov 《Journal of Experimental and Theoretical Physics》2005,100(3):617-634
A method is developed for calculating the equation of state of a system of quantum particles at a finite temperature, based on the Feynman formulation of quantum statistics. A general analytical expression is found for the virial estimator for the kinetic energy of a system with rigid boundaries at a finite pressure. An effective method is developed for eliminating the unphysical singularity in the electrostatic potential between a discretized Feynman path of an electron and a proton. It is shown that the “refinement” of an expansion of a quantum-mechanical propagator by addition of high powers of time exacerbates, rather than eliminates, the divergence of a Feynman path integral. A brief summary of the current status of the problem is presented. The proposed new approaches are presented in relation to progress made in this field. Path integral Monte Carlo simulations are performed for nonideal hydrogen plasmas in which both indistinguishability and spin of electrons are taken into account under conditions preceding the formation of the electron shells of atoms. The electron permutation symmetry is represented in terms of Young operators. It is shown that, owing to the singularity of the Coulomb potential, quantum effects on the behavior of the electron component cannot be reduced to small corrections even if the system must be treated as a classical system according to the formal de Broglie criterion. Quantum-mechanical delocalization of electrons substantially weakens the repulsion between electrons as compared to protons. In relatively cold plasmas, many-body correlations lead to complex behavior of the potential of the average force between particles and give rise to repulsive forces acting between protons and electrons at distances of about 5 angstroms. Plasma pressure drops with decreasing plasma temperature as the electron shells of atoms begin to form, and the electron kinetic energy reaches a minimum at a temperature of about 31000 K. The minimum point weakly depends on plasma density. Owing to quantum effects, the electron component is “heated” well before electrons are completely bound in the field of protons. 相似文献
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Effects of magnetic field on photon-induced quantum transport in a single dot-cavity system
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In this study,we show how a static magnetic field can control photon-induced electron transport through a quantum dot system coupled to a photon cavity.The quantum dot system is connected to two electron reservoirs and exposed to an external perpendicular static magnetic field.The propagation of electrons through the system is thus influenced by the static magnetic and the dynamic photon fields.It is observed that the photon cavity forms photon replica states controlling electron transport in the system.If the photon field has more energy than the cyclotron energy,then the photon field is dominant in the electron transport.Consequently,the electron transport is enhanced due to activation of photon replica states.By contrast,the electron transport is suppressed in the system when the photon energy is smaller than the cyclotron energy. 相似文献
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The Fermi energy, average total kinetic energy density, and also average kinetic energy of finite diamagnetic motion of an
electron gas of specified concentration are calculated. The kinetic energy of continuous longitudinal motion of the electrons
along the direction of an external magnetic field H is determined. It is found that in the quantum limit, when the maximum
Landau quantum number N
m
=0, the kinetic energy of continuous longitudinal motion tends to zero with increase in the external magnetic field strength.
If the maximum Landau quantum number is greater than zero, the longitudinal and transverse kinetic energy components of the
degenerate electron gas change only insignificantly.
Byelorussian State University; Brest State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No.
7, pp. 31–35, July, 1999. 相似文献
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The Fermi energy, density of average kinetic energy, and average density of kinetic energy of the transverse finite motion of an electron gas of a specified concentration are calculated taking into account Landau diamagnetism and Pauli paramagnetism. The kinetic energy of a longitudinal continuous electron motion along the direction of the external magnetic field H is estimated. It is shown that the kinetic energy of the longitudinal continuous motion vanishes with increase in the external magnetic field strength in the quantum limit where the maximum Landau quantum number N
m = 0. For N
m > 0, the longitudinal kinetic energy component of a degenerate electron gas somewhat increases with magnetic field strength. The cause of the erroneous result is discussed. 相似文献
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A. I. Agafonov 《Physics of the Solid State》2011,53(8):1529-1539
A general expression for the cross section of inelastic magnetic scattering of cold polarized neutrons by superconducting
rings has been derived. In this scattering process, the metastable superconducting current changes via quantum jumps corresponding
to a decrease in the number of fluxoids in the superconducting ring by one or several units and the change in the energy of
the ring is transferred to the kinetic energy of the scattered neutron. For rings from type-II superconductors with a thickness
smaller than the field penetration depth but larger than the electron mean free path, the cross sections of inelastic scattering
with neutron spin flip have been obtained for the first time. The possibility of increasing the cross section of neutron scattering
by a system of rings has been discussed. 相似文献
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Nonlinear fluid simulations are developed by us to investigate the properties of fully developed two-dimensional (2D) electron fluid turbulence in a very dense Fermi (quantum) plasma. We find that a 2D quantum electron plasma exhibits dual cascades, in which the electron number density cascades towards smaller turbulent scales, while the electrostatic potential forms larger scale eddies. The characteristic turbulent spectrum associated with the nonlinear electron plasma oscillations (EPO) is determined critically by a ratio of the energy density of the EPOs and the electron kinetic energy density of quantum plasmas. The turbulent transport corresponding to the large-scale potential distribution is predominant in comparison with the small-scale electron number density variation, a result that is consistent with the classical diffusion theory. 相似文献