A framework for understanding molecular ionization in strong laser fields

Abstract

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 oneelectron 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.

Concerted elimination of CH2I2 and CH2ICl under intense femtosecond laser excitation

“…As the laser intensity increases, the transition between the MPI and FI tunnel ionization regimes occurs according to the value of adiabaticity parameter [7]: where IP is the molecular ionization potential in the absence of the laser field, I 0 is the peak intensity and k is the laser wavelength. Values of AP<1 imply the participation of FI mechanism.…”

“…The study of molecules in strong laser fields is a challenging topic in molecular science [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. With the advent of short-pulse lasers the behavior of molecules can be explored on the time scale of vibrational motions.…”

“…Momentum correlation imaging of the atomic fragment ions in intense field was also applied to explore Coulomb explosion dynamics [10]. An important step in the understanding of multiply charged cations has been the discovery of a critical internuclear distance R c , from which multiply ionization preferentially occurs [7].…”

Strong Field Molecular Ionization in the Impulsive Limit: Freezing Vibrations with Short Pulses

“…A detailed understanding of the ionization dynamics is crucial for developing these frontier areas of molecular science [11]. In particular, with a push to improve time resolution in molecular dynamics experiments [12,13], generate multi-hole electron wave packets [14][15][16][17][18] and single attosecond pulses, it is important to understand how ionization depends on the duration of the strongfield driving pulse [19,20]. Here, we study strong-field molecular ionization as a function of pulse duration, going from several tens of fs to below 10 fs, where vibrational dynamics is frozen out (the 'impulsive limit') [21].…”

Multielectron effects in strong-field dissociative ionization of molecules

“…Alternatively, intramolecular electron dynamics can be probed by strong-field ionization (SFI) [4]. The SFI rate reflects strong electron-electron correlation [5] and electron localization [6][7][8][9][10][11], as well as the subsequent dynamics which are responsible for charge symmetric and asymmetric dissociation of multiply ionized molecules [12][13][14].…”