The role of phase in attosecond photoionization experiments: Carbon dioxide as a case study

Speaker:  Daniel Tuthill, Ohio State University

Program Description:
Many table-top observations of attosecond dynamics rely on photoionization, such as in high-harmonic spectroscopy (HHS) or attosecond spectroscopy (AS). However, many of these experiments solely measure the amplitude of the outgoing radiation (HHS) or electron wavepacket (AS) while the phase contains information which amplitudes alone cannot provide. Here I will show two case studies observing attosecond-scale features in CO2 where the phase is key for interpretation. First, I will present HHS results on the well-characterized minimum in the high-harmonic emission of CO2. By measuring the phase of the recombining electron in high-harmonic generation, the source of the minimum, two-center or multiorbital interference, is clearly resolved. Second, I will present AS results measuring the first four cationic states of CO2 where a shape resonance in the C-channel has previously been theoretically predicted but absent from synchrotron amplitude measurements. By measuring the ionization delay, we see an indication of the resonance which may not have been previously observed due to decay through interchannel couplings.