A new look at multi-electron interactions

Attosecond science has opened the door to real-time observation and time domain control of atomic-scale electron dynamics. Study of the electron correlation — electron interactions — through ultrashort laser pulses is ideal for investigating both quantum and classical approaches. The results obtained using both frameworks can be compared with up-to-date experimental results.

Nevertheless, the main advantage of the classical approximation to quantum mechanics is the power law scaling of electron correlation representation with system size. With this in mind, the EU-funded project 'Transition states for multielectron ionization phenomena' (TRANS-MI) seeks to investigate the atomic and molecular processes in strong electron–electron interactions with tools from non-linear dynamics and chemical physics. In particular, TRANS-MI aims to build a framework analogous to the transition state theory for chemical reactions. This should further enhance understanding regarding the role of electron interactions under strong ultrashort laser pulses.

Scientists have found the processes responsible for re-collision–driven non-sequential double ionisation in the presence of a strong, circularly polarised laser field. Based on these results, they have also shown that some key periodic orbits driving the re-collision process are directly linked to the circularly polarised high-harmonic generation. Considering that the conventional re-collision scenario is based on contradictory hypotheses, a purely classical re-collision scenario has been constructed. This modified scenario has been based on a particular periodic orbit that drives the re-collision process.

Another task has been to study dynamics within the transition state for the hydrogen exchange reaction. As the energy increases, the dynamics within the transition state become increasingly chaotic. Scientists have found that the transition state first loses and then, surprisingly, regains its normal hyperbolicity. Therefore, the important phase space structures of transition state theory should exist at most energies above the threshold.

TRANS-MI members have organised workshops and training sessions on a variety of topics to provide a new generation of researchers with a multidisciplinary background. Project results have been published in journals.