Field ionization and Coulomb explosion of CO in an intense femtosecond laser field

The field ionization and Coulomb explosion of diatomic carbon monoxide interacting with intense femtosecond laser pulses was systematically investigated by using a time-of-flight mass spectrometer. The kinetic energy release (KER) in a Coulomb explosion causes the atomic ions to exhibit a double-peak structure. The values of KER calculated using a two-step model were found to agree well with the measured, ones. The distributions of atomic ions are highly anisotropic, having a maximum along the laser polarization axis and a minimum perpendicular to it. In contrast to the atomic ions, the parent ion CO+ exhibits a strong isotropic angular distribution. Suppression of ionization was observed for circularly polarized pulses, indicating that the dynamic alignment is responsible for the observed anisotropic angular distribution of the atomic ions.