Strong field non-Franck–Condon ionization of H2: a semi-classical analysis

• Published in: The European physical journal. ST, Special topics Special topics, 2023, Vol.232 (13), p.2081-2093
• Main Authors: Vigneau, Jean-Nicolas, Atabek, Osman, Nguyen-Dang, Thanh-Tung, Charron, Eric
• Format: Article
• Language: English
• Subjects: Atomic; Atomic Physics; Cations; Circular polarization; Classical and Continuum Physics; Condensed Matter Physics; Ionization; Lasers; Linear polarization; Materials Science; Measurement Science and Instrumentation; Molecular; Optical and Plasma Physics; Physics; Physics and Astronomy; Regular Article; Ultrafast Phenomena from attosecond to picosecond timescales: theory and experiments
• ISSN: 1951-6355; 1951-6401
• DOI: 10.1140/epjs/s11734-022-00750-z

Single ionization of H 2 molecules exposed to strong and short laser pulses is investigated by a semi-classical method. Three laser characteristics are considered: (i) The carrier-wave frequency corresponds to wavelengths covering and bridging the two ionization regimes: From tunnel ionization (TI) at 800 nm to multiphoton ionization (MPI) at 266 nm. (ii) Values of the peak intensity are chosen within a window to eliminate competing double ionization processes. (iii) Particular attention is paid to the polarization of the laser field, which can be linearly or circularly polarized. The results and their interpretation concern two observables, namely the end-of-pulse total ionization probability and vibrational distribution generated in the cation H 2 + . The most prominent findings are an increased ionization efficiency in linear polarization and a vibrational distribution of the cation that favors lower-lying levels than those that would be populated in a vertical (Franck–Condon) ionization, leading to non-Franck–Condon distributions, both in linear and circular polarizations.