Intramolecular electronic dynamics and tunnel ionization of [Formula Presented] in an intense laser field [Formula Presented] and [Formula Presented] are examined with accurate evaluation of three-dimensional two-electron wave-packet dynamics by the dual transformation method. We estimated the ionization probabilities at different values of the internuclear distance R and found that tunnel ionization of [Formula Presented] is enhanced by field-induced two-electron dynamics. An ionic component characterized by the electronic structure [Formula Presented] or [Formula Presented] is created near the descending well, where the dipole interaction energy with the laser electric field [Formula Presented] becomes lower. Ionization proceeds via the formation of a localized ionic component in the descending well, in contrast to the [Formula Presented] case, in which the electron is ejected most easily from the ascending well. As R increases, while the population of [Formula Presented] (or [Formula Presented] decreases, a pure ionic state [Formula Presented] becomes easier to ionize in an intense field because of the smallar attractive force of the distant nucleus. As a result, ionization is enhanced at the critical distance [Formula Presented] [Formula Presented] is the Bohr radius). Although the rate of direct ionization from a covalent state is much smaller than that from an ionic state, the ionization at large R [Formula Presented] mainly proceeds from the remaining covalent component, which outmeasures the created ionic component. Thus, the field-induced intramolecular electron transfer between nuclei, which triggers strong electron-electron correlation, is governed by the molecular structure as well as the field intensity. The mechanism of the ionization enhanced by field-induced intramolecular electron transfer is consistent with the observation of charge-asymmetric dissociation channels of diatomic molecules such as [Formula Presented] We also investigated the intramolecular electronic dynamics by analyzing the populations of field-following adiabatic states defined as eigenfunctions of the instantaneous electronic Hamiltonian. An effective instantaneous Hamiltonian for [Formula Presented] was constructed of three main electronic states, X, [Formula Presented] and [Formula Presented] We found that the difference in electronic and ionization dynamics between the small R and large R cases originates in the character of the level crossing of the lowest two adiabatic states. 5555 2002 The American Physical Society.
|Number of pages||1|
|Journal||Physical Review A - Atomic, Molecular, and Optical Physics|
|Publication status||Published - 2002|
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics