Nonadiabatic strong field ionization of noble gas atoms in elliptically polarized laser pulses.

We present theoretically obtained photoelectron momentum distributions (PMDs) for the strong field ionization of argon in an elliptically polarized laser field at a central wavelength of 400 nm. Three different theoretical approaches, namely, a numerical solution of the time-dependent Schrödinger equation (TDSE), a nonadiabatic model, and a classical-trajectory Monte Carlo (CTMC) model are adopted in our calculations. From the TDSE calculations, it is found that the attoclock offset angle (most probable electron emission angles with respect to the minor axis of the laser's polarization ellipse) in the PMD increases with rising ATI order. While this result cannot be reproduced by the CTMC model, the nonadiabatic model achieves good agreement with the TDSE result. Analysis shows that the nonadiabatic corrections of the photoelectron initial momentum distribution (in both longitudinal and transverse directions with respect to the tunneling direction) and nonadiabatic correction of the tunneling exit are responsible for the ATI order-dependent angular shift.

Laser-Induced Inelastic Diffraction from Strong-Field Double Ionization.

In this Letter, we propose a novel laser-induced inelastic diffraction (LIID) scheme based on the intense-field-driven atomic nonsequential double ionization (NSDI) process and demonstrate that, with this LIID approach, the doubly differential cross sections (DDCSs) of the target ions, e.g., Ar^{+} and Xe^{+}, can be accurately extracted from the two-dimensional photoelectron momentum distributions in the NSDI process of the corresponding atoms. The extracted DDCSs exhibit a strong dependence on both the target and the laser intensity, in good agreement with calculated DDCSs from the scattering of free electrons. The LIID scheme may be extended to molecular systems and provides a promising approach for imaging of the gas-phase molecular dynamics induced by a strong laser field with unprecedented spatial and temporal resolution.

Laser intensity determination using nonadiabatic tunneling ionization of atoms in close-to-circularly polarized laser fields.

We conceive an improved procedure to determine the laser intensity with the momentum distributions from nonadiabatic tunneling ionization of atoms in the close-to-circularly polarized laser fields. The measurements for several noble gas atoms are in accordance with the semiclassical calculations, where the nonadiabatic effect and the influence of Coulomb potential are included. Furthermore, the high-order above-threshold ionization spectrum in linearly polarized laser fields for Ar is measured and compared with the numerical calculation of the time-dependent Schrödinger equation in the single-active-electron approximation to test the accuracy of the calibrated laser intensity.