We present the first numerical simulation of the time delay in the photoionization of the simplest diatomic molecule H + 2 as observed by attosecond streaking. We show that the strong variation of the Eisenbud-Wigner-Smith time delay tEWS as a function of energy and emission angle becomes observable in the streaking time shift tS provided laser field-induced components are accounted for. The strongly enhanced photoemission time shifts are traced to destructive Cohen-Fano (or two-center) interferences. Signatures of these interferences in the streaking trace are shown to be enhanced when the ionic fragments are detected in coincidence.

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The dynamics of photoelectrons ionized by XUV pulses in the presence of a strong infrared (IR) field is theoretically investigated by solving the time-dependent Schrödinger equation (TDSE). We study the ionization dynamics of He by an XUV pulse in the presence of a relatively strong IR laser field, which is different from the conventional attosecond streaking experiments where a rather weak IR field is applied. Comparing with the photoelectron spectra produced by the IR field only, we find the spectra ionized by the combined fields construct interesting interference structures for different XUV photon energies and pulse intensities. These features can be analyzed and explained by a quantum-trajectory theory based on the strong-field approximation (SFA). The SFA theory shows excellent agreement with the TDSE results, revealing that these structures originate from interferences among photoelectrons ionized by XUV pluses (streaked by the strong IR field) at different moments, and in some energy regions, together with the photoelectrons ionized by the intense IR pulse itself.

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We theoretically investigate the low energy part of the photoelectron spectra in the tunneling ionization regime by numerically solving the time-dependent Schrdinger equation for different atomic potentials at various wavelengths. We find that the shift of the first above-threshold ionization (ATI) peak is closely related to the interferences between electron wave packets, which are controlled by the laser field and largely independent of the potential. By gradually changing the short-range potential to the long-range Coulomb potential, we show that the long-range potential's effect is mainly to focus the electrons along the laser's polarization and to generate the spider structure by enhancing the rescattering process with the parent ion. In addition, we find that the intermediate transitions and the Rydberg states have important influences on the number and the shape of the lobes near the threshold.