基于多组态含时Hartree-Fock方法研究电子关联对于H_2分子强场电离的影响

发展了三维的处理双原子分子非微扰电子动力学的多组态含时Hartree-Fock方法,并利用该方法研究了电子关联对于H_2分子强场电离概率的影响.该方法采用能够精确处理双中心库仑势的椭球坐标系,以及减小双电子积分计算量的有限元-离散变量基函数方法.利用多组态含时Hartree-Fock方法计算了H_2分子随分子取向角度变化的XUV光电离结果,并通过与单组态结果的对比研究了电子关联对于单电离和双电离概率的不同影响.研究表明,电子关联对于单电离过程影响很小,而在双电离过程中则发挥了重要作用,导致了电离概率的减小.该方法为进一步研究强场物理过程中的电子关联效应奠定了基础.

Multiconfiguration time-dependent Hartree-Fock treatment of electron correlation in strong-field ionization of H2 molecules

Electron correlation plays an important role in the multielectron interactions of many physical and chemical processes.The investigation of correlation effects in the non-perturbative electronic dynamics (e.g.non-sequential double ionization) when atoms and molecules are subjected to strong laser fields requires non-perturbative theoretical treatments. The direct numerical integration of the time-dependent Schrödinger equation successfully explains many experimental results,but it is computationally prohibitive for systems with more than two electrons.There is clearly a need for a theory which can treat correlation dynamics self-consistently in strong time-dependent electric fields.In this paper we develop a three-dimensional multiconfiguration time-dependent Hartree-Fock method,which can be applied to the non-perturbative electronic dynamics for diatomic molecules,and it can also investigate the effect of electron correlation in strong-field ionization of H₂ molecules.This method adopts the prolate spheroidal coordinates (which can treat the two-center Coulomb potential accurately) and the finite-element method together with discrete-variable representation (which lowers the calculation burden from two-electron integrations).For the temporal propagation,we use the efficient short iterative Lanczos algorithm for the equation which governs the configuration expansion coefficients,while an eight-order Runge-Kutta (RK) method and an Bulirsch-Stoer (BS) extrapolation method,both with adaptive precision controls,are implemented to solve the nonlinear orbital equation.While both methods yield correct results,the BS method displays a better stability in the realtime propagation,while the RK method demands less computation.The alignment-dependent ionization probabilities of H₂ molecules in intense extreme ultraviolet pulses are calculated.Comparisons between multi-configuration and single-configuration results show that electron correlation has little effect on the single ionization process,but it plays an important role in double ionization,leading to the decrease in the ionization probability.The double ionization probability from the single-configuration space 1σ is about three times larger that from 4σ1π.The ionization probability increases monotonically when the alignment angle increases from 0° to 90°, yielding a ratio of 2.6(1.5) between 90° and 0° for the double (single) ionization process.This method presents the basis for the future study of electron correlation in strong-field processes.