Description of molecular dynamics in intense laser fields by the time-dependent adiabatic state approach:: Application to simultaneous two-bond dissociation of CO2 and its control

We theoretically investigated the dynamics of structural deformations of CO2 and its cations in near-infrared intense laser fields (similar to10(15) W cm(-2)) by using the time-dependent adiabatic state approach. To obtain "field-following" adiabatic potentials for nuclear dynamics, the electronic Hamiltonian including the interaction with the instantaneous laser electric field is diagonalized by the multiconfiguration self-consistent-field molecular orbital method. In the CO2 and CO2+ stages, ionization occurs before the field intensity becomes high enough to deform the molecule. In the CO22+ stage, simultaneous symmetric two-bond stretching occurs as well as one-bond stretching. Two-bond stretching is induced by an intense field in the lowest time-dependent adiabatic state 1> of CO22+, and this two-bond stretching is followed by the occurrence of a large-amplitude bending motion mainly in the second-lowest adiabatic state 2> nonadiabatically created at large internuclear distances by the field from 1>. It is concluded that the experimentally observed stretched and bent structure of CO23+ just before Coulomb explosions originates from the structural deformation of CO22+. We also show in this report that the concept of "optical-cycle-averaged potential" is useful for designing schemes to control molecular (reaction) dynamics, such as dissociation dynamics of CO2, in intense fields. The present approach is simple but has wide applicability for analysis and prediction of electronic and nuclear dynamics of polyatomic molecules in intense laser fields.