Observation of Ultrafast electron dynamics in the molecular frame using quantum rotational wave packet

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Time-resolved photoelectron spectroscopy is a powerful means to probe ultrafast electronic dynamics in the molecule. However, the observation is carried out in the laboratory frame, and the information is always convoluted with the broad molecular axis distribution in the laboratory frame. It is ideal to observe the electronic dynamics in the molecular frame, which requires extraction of photoionization dynamical parameters and recasting the photoelectron angular distribution in the laboratory frame into the distribution in the molecular frame. In the past, photoelectron and photoion coincidence method has been employed to extract such information, however, it is only applicable to dissociative ionization. In the present work, we created a rotational wavepacket motion of a molecule and observed photoionization from various time-dependent axis distribution, from which photoelectron angular distribution in the molecular frame has been extracted. The sample molecule was Nitric Oxide, the … More benchmark system in molecular photoionization study. We prepared a rotational wavepacket in the A state of NO by one-photon absorption from the ground state, and then ionized by another photon from the A state. The measurements were carried out on the integral and differential cross sections, and detailed theoretical analysis was performed. We found that the partial wave of outgoing photoelectron is dominated by p-wave contradicting with the prediction of f-wave by theory. It is also pointed out dic wave has appeared with a reasonable intensity whereas theory does not predict it. The existence of the cbt wave is important for describing directional ejection of an electron into either N-side or 0-side of the molecule. We are planning to collaborate further with theoreticians to elucidate the source of this discrepancy between the experiment and theory, thereby improving our understanding of molecular photoionization dynamics and develop a methodology to probe electronic dynamics in the molecular frame. Less