Attosecond photoionization delays in molecules: The role of nuclear motion

Abstract

Molecular photoionization delays are often analyzed by assuming that nuclei remain fixed during the ionization process since they move much more slowly than electrons. However, recent high-energy resolution and multicoincidence experiments have shown that nuclear motion can have a significant and visible effect on the measured ionization delays on the attosecond time scale. To analyze this behavior, we have chosen the simplest of all molecules, H⁺₂, and performed nearly exact calculations of streaking and RABBIT (reconstruction of attosecond beatings by interferences in two-photon transitions) spectra by solving the time-dependent Schrödinger equation in full dimensionality, and retrieved the corresponding photoionization delays. We show that, when two-center effects are at play, nuclear motion is responsible for a substantial increase of the photoionization delays, in particular of the so-called continuum-continuum delays. The magnitude of such an increase is comparable to the absolute values of the measured delays.