Interferences in photo-detached electron spectra from a non-collinear tri-atomic anion

The electron flux oscillations in photo-detachment of a non-collinear tri-atomic anion have been studied by taking each atom of the system as a coherent source of detached-electron wave. These electron waves traversing along three different trajectories result in a quantum interference. An analytical expression of detached-electron flux is evaluated for various detached-electron energies and for different geometrical shapes of the system. The results show that the electron flux distributions exhibit molecular shape-induced oscillatory structures. These oscillations are explained using the semi- classical closed-orbit theory; the outgoing electron waves produced from one center are propagated in the vicinity of the sources at other centers. It is also observed that in a particular case our non-collinear tri-atomic system reduces to the collinear tri-atomic system recently published.     

氢负离子在磁场和金属面附近电子通量分布的研究

利用半经典开轨道理论, 研究了磁场和金属面附近氢负离子的剥离电子通量分布, 并揭示了电子通量分布中的振荡结构与经典轨道之间的关系.固定离子到金属面的距离, 研究了不同的磁场强度对电子通量分布的影响. 结果表明, 由于与电子通量分布相联系的剥离电子的经典轨迹增加, 随着磁场强度的增加, 通量分布变得复杂. 此外发现剥离电子的能量变化也会影响电子通量分布. 因此可以通过改变磁场强度大小和剥离电子的能量来调控剥离电子通量分布和干涉图样. 研究结果对于理解负离子在外场、表面附近的电子流通量和剥离电子干涉图样问题以及将来实验研究负离子的光剥离显微问题都可以提供一定的参考. 关键词： 开轨道理论 电子通量 金属面 磁场     

Interferences in Photodetachment of a Negative Molecular Ion Model

By employing a two-center model, the total and differential cross sections in the photodetachment of ``a negative molecular ion" are studied theoretically and obtained for the case of light polarization parallel to the molecular axis. We find that in contrast to the smooth behavior of the total cross section for perpendicular polarized light, the cross section for parallel polarized light shows an interesting oscillatory structure. The oscillations in the total cross section may provide a method to determine the distance between the two centers. We explain the oscillation in the total cross section as an interference effect using closed-orbit theory. We also calculated the detached-electron flux distributions on a screen placed at a large distance from the negative molecular ion. The distributions display multiple-ring-like interference patterns. Such interference patterns are similar to those in the photodetachment microscopy experiments.     

Coherent quasiclassical dynamics of a persistent current qubit

A new regime of coherent quantum dynamics of a qubit is realized at low driving frequencies in the strong driving limit. Coherent transitions between qubit states occur via the Landau-Zener process when the system is swept through an energy-level avoided crossing. The quantum interference mediated by repeated transitions gives rise to an oscillatory dependence of the qubit population on the driving-field amplitude and flux detuning. These interference fringes, which at high frequencies consist of individual multiphoton resonances, persist even for driving frequencies smaller than the decoherence rate, where individual resonances are no longer distinguishable. A theoretical model that incorporates dephasing agrees well with the observations.     

Oscillations in Total Photodetachment Cross Sections of a Triatomic Anion

The total photodetachment cross section of a linear triatomic anion is derived for arbitrary laser polarization direction. The cross section is ,shown to be strongly oscillatory when the laser polarization direction is parallel to the axis of the system; the oscillation amplitude decreases and vanishes as the angle between the laser polarization and the anion axis increases and becomes perpendicular to the axis. The average cross section over the orientations of the triatomie system is also obtained. The cross section of the triatomic anion is compared with the cross section of a two-center system. We find there are two oscillation frequencies in the triatomie anion in contrast to only one oscillation frequency in the two-center case. Closed-orbit theory is used to explain the oscillations.     

Interferences in Photodetachment of a Negative Molecular Ion

The photodetachment of a negative molecular ion is studied theoretically using a two-center model. The detached electron wave function is obtained as a superposition of two coherent waves originating from each center. The photo-detached electron flux is evaluated on a screen placed at a large distance from the negative molecular ion. The electron flux on the screen displays strong interferences, the peak positions are related to the distance between the two centers in the negative molecular ion. We a/so obtained a simple analytical formula for the total photodetachment cross section. It approaches one and two times of the cross section for the one-center system in the high and lowphoton energy limits respectively.     

Interferences in Photodetachment of a Negative Molecular Ion

The photodetachment of a negative molecular ion is studied theoretically using a two-center model. The detached electron wave function is obtained as a superposition of two coherent waves originating from each center. The photo-detached electron flux is evaluated on a screen placed at a large distance from the negative molecular ion. The electron flux on the screen displays strong interferences, the peak positions are related to the distance between the two centers in the negative molecular ion. We also obtained a simple analytical formula for the total photodetachment cross section. It approaches one and two times of the cross section for the one-center system in the high and low photon energy limits respectively.     

Phase diagram of a two-dimensional square lattice of magnetic particles with perpendicular anisotropy

The ground state of an array of small single-domain magnetic particles having perpendicular anisotropy and forming a square two-dimensional lattice is studied in the presence of a magnetic field. The stability of some basic states with respect to nonuniform perturbations is analyzed in a linear approximation, and analytical model calculations and numerical simulation are used for an analysis. The entire set of states at various anisotropy constants and magnetic fields is considered when a field is normal to the array plane. Two main classes of states are possible for an infinite system, namely, collinear and noncollinear states. For collinear states, the magnetic moments of all particles are normal to the array plane. At a sufficiently high anisotropy, a wide class of collinear states exists. At low fields, a staggered antiferromagnetic order of magnetic moments takes place. An increase in the magnetic field causes an unsaturated state, and this state transforms into a saturated (ferromagnetic) state with a parallel orientation of the magnetic moments of all particles at a sufficiently high field. At a lower anisotropy, the ground state of the system is represented by noncollinear states, which include a complex four-sublattice structure for the components of the magnetic moments in the array plane and a nonzero projection of the magnetic moments of the particles onto the field direction. A phase diagram is plotted for the states of an array of anisotropic magnetic particles in the anisotropy constant-magnetic field coordinates. For a finite array of particles, sample boundaries are shown to play a significant role, which is particularly important for noncollinear states. As a result of the effect of the boundaries at a moderate field or anisotropy, substantially heterogeneous noncollinear states with a heterogeneity size comparable with the sample size can appear in the system.     

Mode Conversion and Diffraction of Guided Optical Waves from Magnetostatic Waves under Inclined Bias Magnetic Field

The noncollinear interaction of guided optical waves with magnetostatic waves under inclined bias magnetic field is theoretically studied in detail. Similar approach can also be applied to the collinear interaction. Calculation results indicate that the diffraction efficiency (DE) in magnitude is equal to the mode-conversion efficiency (MCE) under vertical bias magnetic field, but they differ greatly under inclined bias magnetic field. By comparison to the case of vertical magnetization, the DE or the MCE can be greatly increased under inclined magnetic field. The characteristic of the DE curves obtained is basically in agreement with the experimental result.``     

Problems in using nonlinear collinear processes in third-order acoustical tomography

The processes of acoustical generation of the third-order wave harmonic by nonlinear collinear interaction of the pure third order and the twofold interaction of the second order are considered. It is shown that, in tomography schemes that are based on collinear interaction of waves, the interfering signal considerably exceeds the useful signal that brings information on the acoustical nonlinear parameter of the third order already over short wave propagations. The solutions to the Burgers’ equation and the Riemann waves equation have been numerically modeled to verify theoretical results. It is concluded that, using the nonlinear third-order effects in diagnostics becomes possible only when the tomography schemes are based on the noncollinear interaction of waves.     

Photodetachment microscopy of H~- in the magnetic field near different dielectric surfaces

We study the photo-detachment interference patterns of a hydrogen negative ion in the magnetic field near different dielectric surfaces with a semi-classical open orbit theory.We give a clear physical picture describing the photo-detachment of H-in this case.The electron flux distributions are calculated at various dielectric surfaces with unchanged magnetic field strength.It is found that the electron flux distributions of H-are very different in a magnetic field near different dielectric surfaces,namely the dielectric surface has a great influence on the photo-detachment interference pattern of the negative ion.Therefore,the interference pattern in the detached-electron flux distribution can be controlled by changing the dielectric constant.We hope that our studies may guide the future experimental research in photo-detachment microscopy.     

Magneto-optical spectroscopy with entangled photons

We suggest a way in which entangled photons produced by a type II downconverter can be used for magneto-optical spectroscopy with district advantages. Both collinear and noncollinear geometries can be used. We present quantum mechanical results for the coincidence detection of different polarizations at the output.     

Mode Conversion and Diffraction of Guided Optical Waves from Magnetostatic Waves under Inclined Bias Magnetic Field

The noncollinear interaction of guided optical waves with magnetostatic waves under inclined bias magnetic field is theoretically studied in detail. Similar approach can also be applied to the collinear interaction. Calculation results indicate that the diffraction efficiency (DE) in magnitude is equal to the mode-conversion efficiency (MCE) under vertical bias magnetic field, but they differ greatly under inclined bias magnetic field. By comparison to the case of vertical magnetization, the DE or the MCE can be greatly increased under inclined magnetic field. The characteristic of the DE curves obtained is basically in agreement with the experimental result.     

Relativistic density functional calculations for Pt2

First full-relativistic density functional calculations with the extension of the spin-polarization functional for the relativistic density functional theory in their collinear and noncollinear form are presented here for the molecular system Pt2. The agreement with experiment is very good.     

光子晶体中三能级原子的自发发射

讨论了三能级原子在光子晶体中的自发发射问题.由于量子干涉和光的局域化,两个上能级中的粒子数布居将具有周期振荡或准周期振荡,这不仅依赖于两个上能级与禁带的相对位置, 同时也依赖于原子的初始状态,且有别于真空中三能级原子的自发发射性质. 关键词：     

Tunneling interference of counterpropagating waves in the region of negative magnetic permeability

The interference of two coherent ultrahigh-frequency waves incident normally on opposite faces of a transversely magnetized ferrite layer with negligibly small losses is investigated in the region of negative effective magnetic permeability. It is shown that a coordinate-independent energy flux is formed inside the layer as a result of tunneling interference. The ferrite layer can be made antireflective for appropriate values of the external field and the phases and amplitudes of the incident waves. Zh. Tekh. Fiz. 67, 77–80 (October 1997)     

Interference-induced enhancement of intensity and energy of a quantum optical field by a subwavelength array of coherent light sources

Recently, we have shown a mechanism that could provide great resonant and nonresonant transmission enhancements of the classical (nonquantum) light waves passed through subwavelength aperture arrays in thin metal films not by the plasmon–polariton waves, but by the constructive interference of diffracted waves (beams generated by the apertures) at the detector placed in the far-field zone. We now present a quantum reformulation of the model. The Hamiltonian describing the phenomenon of interference-induced enhancement and suppression of both the intensity and energy of a quantum optical field is derived. The basic properties of the field energy determining by the Hamiltonian are analyzed. Normally, the interference (addition) of two or more waves causes enhancement or suppression of the light intensity, but not the light energy. The model shows that the phenomenon could be observed experimentally, for instance, by using a subwavelength array of the coherent quantum light-sources (one- and two-dimensional subwavelength apertures, fibers, dipoles, and atoms).     

驱动场对光子晶体中原子自发辐射的影响

文章讨论了在驱动场作用下, 三能级原子在光子晶体中的自发辐射问题.由于量子干涉和光的局域化作用,两个上能级中的布居数将具有周期振荡或准周期振荡的性质,这不仅与两个上能级与禁带的相对位置有关,同时也与原子的初始状态有关.驱动场的强度和入射位相也能控制光子晶体中三能级原子的自发辐射.     

好腔中的Bell态原子与纠缠相干态光场相互作用系统的保真度

考虑原子间偶极相互作用,求出好腔中的Bell态原子与纠缠相干态光场相互作用系统的保真度。结果表明,对于理想腔,若原子初始时刻处于相干保持态,系统保真度始终等于1;若原子初始时刻处于其余Bell态之一,腔场初态的平均光子数很小,系统保真度在0～1之间作周期性振荡,随着腔场初态的平均光子数的增加,系统保真度的振荡频率增大,振幅减小。对于好腔,若原子初始时刻处于相干保持态,系统保真度呈指数单调衰减;若原子初始时刻处于其余Bell态之一,系统保真度呈指数振荡衰减,且随着腔场初态的平均光子数的增加,系统保真度的振荡频率增大,振幅减小。     

好腔中的Bell态原子与纠缠相干态光场相互作用系统的保真度

考虑原子间偶极相互作用,求出好腔中的Bell态原子与纠缠相干态光场相互作用系统的保真度.结果表明,对于理想腔,若原子初始时刻处于相干保持态,系统保真度始终等于1;若原子初始时刻处于其余Bell态之一.腔场初态的平均光子数很小,系统保真度在0～1之间作周期性振荡,随着腔场初态的平均光子数的增加,系统保真度的振荡频率增大,振幅减小.对于好腔,若原子初始时刻处于相干保持态,系统保真度呈指数单调衰减;若原子初始时刻处于其余Bell态之一,系统保真度呈指数振荡衰减,且随着腔场初态的平均光子数的增加,系统保真度的振荡频率增大,振幅减小.