ETH Library Linked Attosecond Phase Interferometry for Molecular Frame Measurements

High-harmonic spectroscopy utilizes attosecond techniques to measure single-atom or molecule photorecombination cross sections [1–4]. While the amplitude of the extreme ultraviolet (XUV) light can be easily measured, the phase is much more challenging to access, yet it contains information about the attosecond synchronization of electron recollision dynamics [5], the instantaneous ionization potential [6], the photorecombination dipole moment [7], and the role of a possible ionization phase [8, 9]. In particular, knowledge of the recombination phase is necessary for tomographic imaging of the molecular orbital wave function with attosecond-Ångström resolution [10–13]. Present techniques [14, 15] cannot simultaneously measure the phase as a function of molecular angle and photon frequency, which is necessary for a full reconstruction of the wave function. We overcome this limitation with a new all-optical method. We apply it to record the full phase map of aligned bromine molecules relative to reference xenon atoms. It allows us to resolve, both spectrally and angularly, the participation of multiple molecular orbitals, and infer a phase of ionization.