XUV ionization of the H2_2 molecule studied with attosecond angular streaking

We study orientation and two-center interference effects in attosecond time-resolved photoionization of the H$_2$ molecule. Time resolution of XUV ionization of H$_2$ is gained through the phase retrieval capability of attosecond angular streaking demonstrated earlier by Kheifets {\em et al} [arXiv:2202.06147 (2022)]. Once applied to H$_2$, this technique delivers an anisotropic phase and time delay which both depend sensitively on the molecular axis orientation. In addition, the photoelectron momentum distribution displays a very clear two-center interference pattern. When the interference formula due to Walter and Briggs [J. Phys. B {\bf 32} 2487 (1999)] is applied, an effective photoelectron momentum appears to be greater than the asymptotic momentum at the detector. This effect is explained by a molecular potential well surrounding the photoemission center.Comment: 8 pages, 7 figure

Wave packet evolution approach to ionization of hydrogen molecular ion by fast electrons

The multiply differential cross section of the ionization of hydrogen molecular ion by fast electron impact is calculated by a direct approach, which involves the reduction of the initial 6D Schr\"{o}dinger equation to a 3D evolution problem followed by the modeling of the wave packet dynamics. This approach avoids the use of stationary Coulomb two-centre functions of the continuous spectrum of the ejected electron which demands cumbersome calculations. The results obtained, after verification of the procedure in the case atomic hydrogen, reveal interesting mechanisms in the case of small scattering angles.Comment: 7 pages, 8 Postscript figure

Numerical attoclock on atomic and molecular hydrogen

Numerical attoclock is a theoretical model of attosecond angular streaking driven by a very short, nearly a single oscillation, circularly polarized laser pulse. The reading of such an attoclock is readily obtained from a numerical solution of the time-dependent Schr\"odinger equation as well as a semi-classical trajectory simulation. By making comparison of the two approaches, we highlight the essential physics behind the attoclock measurements. In addition, we analyze the predictions of the Keldysh-Rutherford model of the attoclock [Phys. Rev. Lett. 121, 123201 (2018)]. In molecular hydrogen, we highlight a strong dependence of the width of the attoclock angular peak on the molecular orientation and attribute it to the two-center electron interference. This effect is further exemplified in the weakly bound neon dimer.Comment: 8 pages, 7 figure