Charge-resonance-enhanced ionization of molecular ions in intense laser pulses: Geometric and orientation effects

Numerical solutions of the time-dependent Schr\"odinger equation for one-electron two-dimensional H₂⁺, H₃²⁺ molecular ions have been obtained in order to illustrate the dependence of charge-resonance-enhanced ionization (CREI) on the angular orientation of the molecule. For H₃²⁺ both linear and triangular geometries have been considered. It is found, in general, that orientational effects on ionization rates, laser-induced dipole moments and torques, are most significant at the critical distances Rc and critical angles φc of molecular geometry where CREI occurs. The calculated ionization rates and field-induced torques are used to estimate alignment times near the dissociative ionization regime of these ions in intense laser pulses. It is found that orientational trapping can occur in this regime at the critical CREI configurations.