We study time-dependent populations in the excited states of many-electron atoms and molecules with the multiconfiguration time-dependent Hartree–Fock method and reveal the non-stationary behavior of the excited-state populations during field-free propagation originating from the nonlinear character of the equations of motion. We calculate the time-dependent populations of the three lowest singlet S states in a helium atom for two different cases of intense laser-atom interaction. In the first case, He is excited by a VUV pulse with the central wavelength of 108 nm, which is two-photon resonant with the ##IMG## [http://ej.iop.org/images/0953-4075/53/10/105601/jpbab7c3bieqn1.gif] {${}^{1}S\,1s3s\leftarrow {}^{1}S\,1{s}^{2}$} transition. In the second case, He is excited by an off-resonant UV laser pulse with the central wavelength of 200 nm. We obtain the stationary wave functions of the excited states by imaginary time propagation and show that the p...

中文翻译：

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多配置时变Hartree-Fock方法中的激发态种群

我们使用多配置时变Hartree-Fock方法研究了多电子原子和分子的激发态中的时变种群，并揭示了由于非线性特征而引起的无场传播过程中激发态种群的非平稳行为运动方程。对于两种不同的强烈激光-原子相互作用情况，我们计算了氦原子中三个最低单重态S状态的时间依赖性种群。在第一种情况下，他被具有108 nm中心波长的VUV脉冲激发，该中心波长与## IMG ## [http://ej.iop.org/images/0953-4075/ 53/10/105601 / jpbab7c3bieqn1.gif] {$ {} ^ {1} S \，1s3s \ leftarrow {} ^ {1} S \，1 {s} ^ {2} $}过渡。在第二种情况下，He被中心波长为200 nm的非共振UV激光脉冲激发。