An investigation of the dynamics of the ionization/dissociation in SF6 with femtosecond pulses

Abstract

We systematically investigated the ionization and dissociation of SF6 in strong laser fields. The dependence of ion yield on laser intensity and the kinetic energy distributions and angular distributions of fragment ions were also measured. The observed sequence of fragment ions is consistent with the predictions of strong-field ionization theory. The kinetic energy distributions of the Fq+ (q = 1–3) fragment ions are presented. Using a point charge model, we propose that the structure-symmetric dissociation (SSD) explains the origin of the kinetic energy of Fq+ ions. Furthermore, we identify the relevant channels and the kinetic energies of the Fq+ fragment ions produced by these channels. These results are in excellent agreement with the experimental data. The angular distributions of the Fq+ and Sq+ (q = 3, 5) ions are all anisotropic and isotropic, respectively. This is the result of the SSD process of the parent ion. However, the anisotropic component in the angular distribution of SFn+ (n = 1–4), SFn2+ (n = 2, 4), and Sq+ (q = 1, 2) suggests that the molecular structure has undergone deformation by the presence of the laser field. A comparison of the time-of-flight (TOF) spectra of fragment ions under linearly polarized and circularly polarized laser fields reveals that the SF6 molecule exhibits negligible dynamic alignment in the laser field, with geometric alignment being the dominant mechanism. Furthermore, the rescattering process plays a significant role in the production of SFn2+ (n = 2, 4) ions. The dynamics of the ionization/dissociation mechanism are discussed in the context of the TOF mass spectra, kinetic energies, and angular distributions recorded for SF6.