A framework for understanding molecularionization in strong laser fields

Abstract

The aim of this paper is to examine the role of excited statesand multi-electron interactions in molecular ionization bystrong laser fields. We present new data on the ionization anddissociation of iodine molecules that reveal important aspectsof the strong field-molecule interaction in the short pulseregime. Our data, along with previous studies, is inconsistentwith the simplest and commonly accepted model of molecular ionization in a strong laser field and this has led us toexamine closely the individual ionization steps. We have foundthat a molecule can ionize into several distinct configurationspredominantly through multi-electron interactions and theabundance of such configurations is dependent on internuclearseparation. The ionization appears to be dominated by pairs of states with gerade and ungerade symmetry, as they have a largedipole coupling and the transition is near resonant with thestrong laser field. In a one-electron molecule, this pairconsists of the ground and first excited state whereas in atwo-electron molecule this corresponds to the lowest lying pairof ionic states. In this paper, we propose a framework for organizing the numerous ionization pathways based on theelectronic configuration of the initial charge state.