Two-electron atoms in superintense radiation fields: Dichotomy and stabilization
The high-frequency Floquet theory describing the interaction of a two-electron atom with a linearly polarized laser field is applied to the case when the characteristic parameter a0=E0w-2 a.u. is large, corresponding to the dichotomy regime of the one-electron problem. We first revisit this case and extend the large- a0 energy-level formula obtained earlier to higher order in a0-1. We then prove the existence of a dichotomy regime also for the two-electron atom, characterized by the two electrons being situated in disjoint electronic clouds separated by an average distance of 2a0. We obtain the first four terms in the expansion of the related energy-level formula in fractional powers of a0-1. The coefficients entering this expansion have been expressed in terms of the eigenvalues of a nonseparable Schrödinger equation containing the end-point potential and of integrals over its eigenfunctions. The equation was solved using the finite element method. An infinite sequence of levels emerges. In the case of H- this implies the existence of a large number of light-induced excited states, some of them corresponding to two-electron excitations not subject to autodetachment. Finally, we prove that in the dichotomy regime a two-electron atom undergoes stabilization and that the ionization rates are essentially twice those for a one-electron atom with the same nuclear charge.
|Journal||Phys. Rev. A|
Gavrila, M, & Shertzer, J. (1996). Two-electron atoms in superintense radiation fields: Dichotomy and stabilization. Phys. Rev. A, 53, 3431–3443.