Attosecond XUV-IR pump-probe measurements of small molecules using 3D momentum spectroscopy

Abstract

The thesis reports on experiments conducted at a beamline combining a high-order harmonic generation-based attosecond pulse source operating at 100 kHz with an electron-ion coincidence detector (Reaction Microscope). The beamline is driven by a noncollinear optical parametric chirped pulse amplification system, in which few-cycle near infrared pulses generated by a titanium sapphire oscillator are amplified using the picosecond laser pulses delivered by a ytterbium-YAG pump laser. The reported beamline is designed for extreme ultraviolet–near infrared pump-probe experiments either with attosecond pulse trains or isolated attosecond pulses.

A series of time-resolved measurements with attosecond pulse trains were performed in molecular nitrogen focusing on the predissociative ionic C state. The corresponding ultrafast photoelectron dynamics was accessed with vibrational resolution. The performed investigation revealed a non-trivial energy dependence of extracted photoionization delays with respect to a noble gas reference. The observed effect could be a consequence of the multi-electron character of the photoinduced process under investigation. The reported results are manifesting one more step towards the attosecond spectroscopy of large complex molecules with coincidence detection.