Intramolecular electron dynamics in the ionization of acetylene by an intense laser pulse.

Ionization of acetylene (C2H2) induced by an intense laser field whose polarization direction is parallel to the molecular axis is investigated by time-dependent Hartree-Fock calculations. It is found that, in the ionization process, the probability of the ejection of an electron from the two highest occupied orbitals of σ symmetry increases drastically as the C-H distance is symmetrically increased. On the contrary, the ejection probability of an electron in the two degenerate π orbitals is much less influenced by the bond elongation. The laser-induced dynamics of the time-dependent orbitals are interpreted by projecting them onto time-independent orbitals, which are eigenfunctions of the time-independent Fock operator.