Asymmetric Dissociative Tunneling Ionization of Tetrafluoromethane in - 2 Intense Laser Fields.

Dissociative ionization of tetrafluoromethane (CF) in linearly polarized -2 ultrashort intense laser fields (1.4 × 10 W/cm, 800 and 400 nm) has been investigated by three-dimensional momentum ion imaging. The spatial distribution of produced by CF → + 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 and 2 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 -2 electric fields tends to be broken. Weak-field asymptotic theory (WFAT) shows that the tunneling ionization from the 4 second highest-occupied molecular orbital (HOMO-1) surpasses that from the 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.