用Coulomb-Volkov方法研究强激光场中H原子的电离

利用Coulomb-Volkov方法研究了H原子在不同波长的线性极化强激光场中电离的能量谱和动量谱,并与强场近似和直接数值求解含时Schr(o|¨)dinger方程的结果进行比较,结果发现:随着激光频率的增加,由Coulomb-Volkov方法得到的结果与数值求解含时Schr(o|¨)dinger方程的结果符合得很好.     

Electronic structure of the ideal silicon vacancy by the muffin-tin green's function method

The muffin-tin Green's function method is applied to the ideal vacancy in silicon in the extended-charge single site approximation. The characteristics of the partially occupied gap state are found to be strongly dependent on the extent of the charge perturbation outside of the vacancy muffin-tin.     

用强场近似方法研究强激光场中H原子的电离

利用传统的强场近似方法和考虑Coulomb修正的强场近似方法,计算了H原子在激光场中的总电离几率及H原子在不同波长激光场中电离的能量谱,并将得到的能量谱与直接数值求解含时Schrödinger方程的结果进行了比较,结果发现：当激光波长较长时,考虑Coulomb 修正的强场近似方法得到的结果与数值求解含时Schrödinger方程的结果符合得较好。     

超快强激光驱动的原子分子电离

强场电离是超快强激光与物质相互作用时发生的基本物理过程。强场驱动原子分子的电离电子动力学过程发生在一个光学振荡周期以内,是在阿秒时间尺度上研究电子超快动力学的典范。不仅如此,强场驱动下的超短电子束还为探测原子分子的结构及其超快动力学提供了重要的技术手段。文章首先简要阐述了超快强光场中原子分子电离的基本物理图像,在此基础上,介绍了近年来基于强场电离电子开展的超快过程研究的几个例子,最后简要讨论了强场电离研究的未来可能发展方向。     

Ti+2 impurity states in ZnSe by the green's function method

A generalization of the molecular multiple scattering method to potentials consisting of a muffin-tip potential plus a spherically symmetric potential is used in calculations of the electronic structure of titanium impurity in zinc selenide. The results are compared with that obtained by the usual multiple-scattering method and with available experimental data.     

On the semiclassical green's function in the energy-representation

We present a detailed discussion of the semiclassical approximation for the Green's function in the energy representation, G(qⁱ,q^j; E). In particular, we describe the way in which classical catastrophes influence the semiclassical approximation, and present a practical scheme to determine the phases with which the contributions due to the various classical trajectories enter the semiclassical result.     

Geometric dependence of casimir energy and scalar green's functions

It is well known that the Casimir Energy depends on the geometry of the conducting cavity. In this note, scalar Green's functions are used to determine the Casimir energy's dependence on terms bilinear in the extrinsic curvatures of the cavity's surface, and thus to resolve the controversy over the Casimir energy's finiteness.     

Binary collision expansion and partial green's functions of Kadanoff-Baym

A new formula for the binary collision expansion of the unitary operator U (t₂, t₁) is proposed. The formula is applied to the expansion of the partial Green's functions of Kadanoff-Baym in powers of the correct binary scattering amplitude. It is shown that certain linked diagrams of left-multidentate structure should be taken into account. The duration of the binary collision is seen to play an important role in the rigorous formulation. Upon neglecting this duration, a useful approximation is found for the analysis of correlations on a macroscopic time scale.     

Stabilization of hydrogen atom in intense laser fields

The stabilization of real hydrogen atom rather than the model under the influence of high frequency superstrong laser pulse is investigated by numerical integration of time-dependent Schrödinger equation. The target wavefunctions are expanded in terms of a discrete L² basis. The evidence of stabilization as found by Su et al. for 1D model atom using the split operator technique has been confirmed for the hydrogen atom using L² technique.     

Higher order field equations II; Limit properties of green's functions

In a previous paper wave propagation was studied according to a sixth-order partial differential equation involving a complex mass M. The corresponding Yang-Feldman integral equations (indicated as SM-YF-equations), were formulated using modified Green's functions G^M_R(x) and G^M_A(x), which then incorporate the partial differential equation together with certain boundary conditions. In this paper certain limit properties of these modified Green's functions are derived: (a) It is shown that for |M| → ∞ the Green's functions G^M_R(x) and G^M_A(x) approach the Green's functions Δ_R(x) and Δ_A(x) of the corresponding KG-equation (Klein-Gordon equation). (b) It is further shown that the asymptotic behaviour of G^M_A(x) and G^M_A(x) is the same as of Δ_R(x) and Δ_A(x) - and also the same as for D_R(x) and D_A(x) for t→ ± ∞, where D_R and D_A are the Green n's functions for the KG-equation with mass zero. It is essential to take limits in the sense of distribution theory in both cases (a) and (b). The property (b) indicates that the wave propagation properties of the SM-YF-equations, the KG-equation with finite mass and the KG-equation with mass zero are closely related in an asymptotic sense.     

A classical green's function approach to vibrational spectra of biopolymers

Classical green's function methods can be used to calculate the spectra of large molecules by essentially putting together the spectra of smaller parts. The methods are useful where the parts are connected by few valence bonds.     

用伪谱方法计算强激光场中一维原子的阈上电离谱

引入非线性空间变换,用伪谱方法求解了一维原子在强激光场中的薛定谔方程,再利用B样条函数和傅立叶级数的线性组合构造原子未微扰的本征函数,计算了一维原子在强激光场中的阈上电离谱,其结果与分裂算符法得到的结果符合得很好.     

Dissociative ionization of molecules in intense laser fields

Accurate and efficient grid based techniques for the solution of the time-dependent Schrödinger equation for few-electron diatomic molecules irradiated by intense, ultrashort laser pulses are described. These are based on hybrid finite-difference, Lagrange mesh techniques. The methods are applied in three scenarios, namely H₂ ⁺ with fixed internuclear separation, H₂ ⁺ with vibrating nuclei and H₂ with fixed internuclear separation and illustrative results presented.Received: 19 November 2002, Published online: 24 April 2003PACS: 02.60.Cb Numerical simulation; solution of equations - 02.70.Bf Finite-difference methods - 33.80.Rv Multiphoton ionization and excitation to highly excited states (e.g., Rydberg states) - 33.80.-b Photon interactions with molecules     

Saturated ionization of fullerenes in intense laser fields

We investigate the ionization of icosahedral fullerenes (C20, C60, C80, and C180) in an intense laser pulse using the S-matrix theory. The results obtained are in excellent agreement with the recent observations of unexpectedly high saturation intensities of the Buckminster fullerene and its multiply charged ions. Our analysis strongly suggests that the related phenomenon of suppressed ionization of these complex fullerenes is due to the finite cage size and the "multislit" interference effect between partial waves emitted from the different nuclei rather than to a dynamical multielectron polarization effect.     

Selection rules for atom multiphoton ionization by intense light in a non-perturbative theory

Using a non-pertubative theoretical analysis we establish the selection rules for the multiphoton ionization effect in hydrogen-like atoms by intense linearly and circularly polarized light, alternatively. No approximations are carried out during these calculations and the obtained results are more general than those obtained to date.     

Functional approach to the parametric derivatives of renormalized green's functions with multiple insertions

Functional derivation of formulae for parametric derivatives of renormalized Green's functions with multiple insertions of composite operators is presented. An application to the derivative with respect to the ultraviolet cutoff in the Pauli–Villars regularized ?⁴₄ theory is given.     

Effect of electron excitation in nonsequential double ionization by intense laser fields

We study the double ionization process of atoms in intense laser fields. The momentum distributions of the correlated electrons are calculated. Contrary to the general expectation, we show an increasing proportion of the electrons ionized via excitation with the increasing laser intensity. These electrons generally have small energy thus they concentratedly distribute on the central region of the momentum diagram. Consequently, the central part of the momentum diagram becomes more notable in higher intensity laser fields. Further study suggests that this phenomenon is general in double ionization.