Photoionization interferometry
Laboratory frame photoelectron spectra are interferograms with both intrinsic molecular and experimentally controllable characteristics. We propose a general time-domain approach to completely determine the amplitude and phase of all contributing photoionization matrix elements. First, a rotational wavepacket is generated on the ground state of the molecule by stimulated Raman scattering. Laboratory frame angle-resolved photoelectron spectra are then recorded as a function of the delay over a full revival period by a velocity map imaging spectrometer. In a first fitting procedure, axis distribution moments up to 6th order are extracted from the observables using comparisons with time-domain Schrodinger equation for the non-adiabatic femtosecond molecular alignment. In a second fitting procedure, the full set of molecular frame photoionization matrix elements is retrieved using the axis distribution moments and the laboratory frame photoelectron angular distributions. Reconstructed molecular frame photoelectron angular distributions are then compared with ab initio calculations. We demonstrate this technique for three cationic channels of the nitrogen molecule probed by 23.3 eV photons.
C. Marceau, V. Makhija, D. Platzer, A. Yu. Naumov, P. B. Corkum, A. Stolow, D. M. Villeneuve, P. Hockett, Bootstrapping to the Molecular Frame with Time-domain Photoionization Interferometry, arXiv:1701.08432.