Asymmetric Dissociative Tunneling Ionization of Tetrafluoromethane in ω − 2ω Intense Laser Fields

• Published in: Frontiers in chemistry Vol. 10; p. 857863
• Main Authors: Hasegawa, Hiroka, Walmsley, Tiffany, Matsuda, Akitaka, Morishita, Toru, Madsen, Lars Bojer, Jensen, Frank, Tolstikhin, Oleg I., Hishikawa, Akiyoshi
• Format: Journal Article
• Language: English
• Published: Frontiers Media S.A 14.04.2022
• Subjects: Chemistry; coherent control; intense laser fields; molecular dissociation; tetrafluoromethane; tunneling ionization
• ISSN: 2296-2646; 2296-2646
• DOI: 10.3389/fchem.2022.857863

Dissociative ionization of tetrafluoromethane (CF 4 ) in linearly polarized ω -2 ω ultrashort intense laser fields (1.4 × 10 14  W/cm 2 , 800 and 400 nm) has been investigated by three-dimensional momentum ion imaging. The spatial distribution of C F 3 + produced by CF 4 → C F 3 + + F + e − exhibited a clear asymmetry with respect to the laser polarization direction. The degree of the asymmetry varies by the relative phase of the ω and 2 ω laser fields, showing that 1) the breaking of the four equivalent C-F bonds can be manipulated by the laser pulse shape and 2) the C-F bond directed along the larger amplitude side of the ω -2 ω electric fields tends to be broken. Weak-field asymptotic theory (WFAT) shows that the tunneling ionization from the 4 t 2 second highest-occupied molecular orbital (HOMO-1) surpasses that from the 1 t 1 HOMO. This predicts the enhancement of the tunneling ionization with electric fields pointing from F to C, in the direction opposite to that observed for the asymmetric fragment ejection. Possible mechanisms involved in the asymmetric dissociative ionization, such as post-ionization interactions, are discussed.