We present a simple exact analytical solution, using the Weyl-Titchmarsh-Kodaira spectral theorem, for the spectral function of the one-dimensional diatomic molecule model consisting of two attractive delta function wells in the presence of a static external electric field. For sufficiently deep and far apart wells, this molecule supports both an even and an odd state, and the introduction of a static electric field turns these bound states into quasi-bound states which are Stark shifted and broadened. The continuum spectrum also inherits an intricate pattern of resonances which reflect the competition between resonant scattering between the two atomic wells and between the linear potential and one or both atomic well(s). All results are analytic and can be easily plotted. The relation between the large orders of the divergent perturbative Stark shift series and the non-perturbative widths of quasi-bound levels is studied.
Ionization of molecular hydrogen and deuterium by a frequency-doubled Ti:sapphire laser pulses
在$(2-13)\times10^{13} $ W cm $^{-2}$的强度范围内，对平行或垂直于线偏振激光脉冲（400 nm）的氢或氘分子的强场单电离进行了理论研究.该研究是基于非微扰处理，解决了完整的时间依赖的薛定谔方程的相关电子内固定的核和偶极子近似。各种核间分离的结果被用来获得分子氢和氘在其基态振动态的电离产额。一个原子模型是用来识别的影响，内在的双原子两中心字符的问题。
Influence of molecular symmetry on strong-field ionization: Studies on ethylene, benzene, fluorobenzene, and chlorofluorobenzene
利用分子强场近似，我们考虑了分子对称性对强线偏振激光脉冲电离分子的影响。电子角分布和总电离产率计算作为分子和激光偏振之间的相对取向的函数。我们的研究集中在乙烯（C $_2$ H $_4$）、苯（C $_6$ H $_6$）、氟苯（C $_6$ H $_5$ F）和邻氯氟苯（1，2 C $_6$ H $_4$ ClF），这些分子代表四种不同的点群。实验结果进行了比较，当可用时，并与适当扩展到非线性多原子分子的分子隧穿理论。我们的研究表明，电离产率的取向依赖性主要是由节点表面结构的分子轨道。
A molecular rotation assisted non-sequential double ionization (MR-NSDI) mechanism is identified in the breakup of rotational H$_2$ molecules in a few-cycle intense laser pulse using a semi-classical trajectory Monte Carlo method. Applying a molecular source in an appropriate rotational state could intensively boost NSDI probability, and conclude with an additional small anti-correlated electron momentum distribution. It reveals the critical role of the continuous dynamics of molecular rotation, which assists the recollision process and subsequently releases the excited electron from the poten…
We investigate the photoelectron angular emission distributions obtained by strong field dissociative ionization of H$_2$ using cold target recoil ion momentum spectroscopy. In case of employing laser light with an ellipticity close to 0.9 and an intensity of 1.0 $\times$ 10$^{14}$ W/cm$^2$, we find that the most probable release-time of the electron does not generally coincide with the time when the laser field maximizes. The release-time is affected by the molecular orientation. In addition, we observe that the width of the release-time distribution depends on molecular orientation. We attri…
The attosecond ultrafast ionization dynamics of correlated two- or many-electron systems have, so far, been mainly addressed investigating atomic systems. In the case of single ionization, it is well known that electron-electron correlation modifies the ionization dynamics and observables beyond the single active electron picture, resulting in effects such as the Auger effect or shake-up/down and knock-up/down processes. Here, we extend these works by investigating the attosecond ionization of a molecular system involving correlated two-electron dynamics, as well as non-adiabatic nuclear dynam…
On Orientation Dependence of N2 Ionization: The Velocity Gauge Version of Molecular Strong-Field Approximation
我们对T. K. Kjeldsen和L. B. Madsen [e-print arXiv：physics/0508213]，并承认他们对我们的3 σ_g分子态模型的不完美组成的批评[V.I. Usachenko和S.- I. Chu，Phys.Rev.A71，063410（2005）]。然而，我们不能同意作者提出的这一批评也是一个无可辩驳的论点和/或证据，支持和证明他们的相反和不正确的（即与相关实验不一致）N2电离率的取向依赖性内计算的速度计版本的分子强场近似。我们揭示了矛盾的真正原因，并证明了适当组成的3sigma_g态（根据评论的评论修改），而不是证实了替代早期的计算[A. Jaron-Becker，A. Becker和F. H. M. Faisal，Phys.Rev.A69，023410（2004）]，这表明N2电离的正确取向依赖性，与该评论的作者应用3 σ_g组成的相同方法和程序的相应结果相反。
The double-slit interference in single-photon ionization of the diatomic molecular ion $\mathrm{H}_2^+$ is theoretically studied beyond the dipole approximation. Via simulating and comparing the interactions of the prealigned $\mathrm{H}_2^+$ and the hydrogen atom with the xuv pulses propagating in different directions, we illustrate two kinds of effects that are encoded in the interference patterns of the photoelectrons from $\mathrm{H}_2^+$: (i) the photon-momentum transfer and (ii) the finite speed of light. While both effects could modify the maxima of the interference fringes, we show tha…
We show that the combination of two achiral components - atomic or molecular target plus a circularly polarized photon - can yield chirally structured photoelectron angular distributions. For photoionization of CO, the angular distribution of carbon K-shell photoelectrons is chiral when the molecular axis is neither perpendicular nor (anti-)parallel to the light propagation axis. In photo-double-ionization of He, the distribution of one electron is chiral, if the other electron is oriented like the molecular axis in the former case and if the electrons are distinguishable by their energy. In b…
Visualizing intense laser field driven electron dynamics in a multielectron molecule: dynamic electron localization, bonding properties and multiple ionization bursts
We discuss the mechanism by which the inclusion of multielectron polarization improves the solution of the time-dependent Schrödinger equation (TDSE) for the oriented CO molecule in a strong external laser pulse within the single-active-electron (SAE) approximation. A challenging problem of using the SAE approximation is that the active electron, instead of undergoing ionization, may be driven by the external field to lower-lying orbitals. For the oriented CO molecule, dipole coupling to the lower-lying bound states of the potential depends on the orientation angle, thereby affecting the orien…
Chiral molecules ionized by circularly polarized fields produce a photoelectron current orthogonal to the polarization plane. This current has opposite directions for opposite enantiomers and provides an extremely sensitive probe of molecular handedness. Recently, such photoelectron currents have been measured in the strong-field ionization regime, where they may serve as an ultrafast probe of molecular chirality. Here we provide a mechanism for the emergence of such strong-field photoelectron currents in terms of two propensity rules that link the properties of the initial electronic chiral s…
In this paper we study the ionization rate and the Stark shift of a one-dimensional model of the H$_{2}^{+}$ ion. The finding of these two quantities is reduced to the solutions of a complex eigenvalue problem. We solve this problem both numerically and analytically. In the latter case we consider the regime of small external electrostatic fields and small internuclear distances. We find an excellent agreement between the ionization rate computed with the two approaches, even when the approximate result is pushed beyond its expected validity. The ionization rate is very sensitive to small chan…
Strong-field photoelectron momentum imaging of the prototypical biomolecule indole was disentangled in a combined experimental and computational approach. Experimentally, strong control over the molecules enabled the acquisition of photoelectron momentum distributions in the molecular frame for a well-defined, narrow range of incident intensities. A novel, highly efficient semiclassical simulation setup based on the adiabatic tunneling theory quantitatively reproduced these results. Jointly, experiment and computations revealed holographic structures in the asymptotic momentum distributions, w…
An apparatus for production of various atomic and molecular ions inside a linear Paul trap has been set up. The system applies a custom-made, low energy, pulsed electron gun to produce ions in electron impact process. Such ionization method can find some interesting possible applications such as derivation of ions inaccessible other-ways, which can be used in molecular ion experiments. The technique allows also for determination of cross sections for various collisional processes. As a feasibility study, the apparatus was used for determination of ionization integral cross section of calcium i…
We study propagation effects due to the finite speed of light in ionization of extended systems. We present a general quantitative theory of these effects and show under which conditions such effects should appear. The finite speed of light propagation effects are encoded in the non-dipole terms of the time-dependent Shrödinger equation and display themselves in the photoelectron momentum distribution projected on the molecular axis. Our numerical modeling for the \Hp molecular ion and the \Ne dimer shows that the finite light propagation time from one atomic center to another can be accuratel…
