Imaging electron molecular orbitals via ionization by intense femtosecond pulses

We report an ab initio investigation of the ionization of an oriented molecule (H₂⁺) by intense linearly polarized laser pulses, using initial states (i.e., the active orbitals) having various symmetries and electron distributions. We show that the orientation dependence of the total (nondifferential) ionization probability of a molecule is very sensitive to the electron distribution within the active orbital. This sensitivity is strong enough that by collecting the ionization probability for various molecular orientations relative to the laser polarization, one can infer the electron distribution within the active orbital. The ionization of oriented molecules by intense low frequency fields can be a tool for imaging electron densities in active molecular orbitals.