A framework for understanding molecular ionization in strong laser fields

The aim of this paper is to examine the role of excited states and multi-electron interactions in molecular ionization by strong laser fields. We present new data on the. ionization and dissociation of iodine molecules that reveal important aspects of the strong field-molecule interaction in the short pulse regime: Our data,along with previous studies, is inconsistent with the simplest and commonly accepted model of molecular ionization in a strong laser field and this has led us to examine closely the individual ionization steps. We have found that a molecule can ionize into several distinct configurations predominantly through multi-electron interactions and the abundance of such configurations-is-dependent on internuclear separation: The ionization appears to be dominated by pairs of states With gerade and ungerade symmetry, as they have a large dipole coupling and the transition is near resonant with the strong laser field. In a one-electron. electron molecule, this pair consists of the ground and first excited state whereas in a two-electron molecule this corresponds to the lowest lying. pair of ionic states. In this paper, we propose a framework for organizing the numerous ionization pathways based on the-electronic configuration of the initial charge state.