Relativistic Multichannel Theory: Doubly Excited States of Atomic Helium

In the report, the recently developed relativistic multichannel theory (RMCT) is a full relativistic non-perturbative method and can be applied to the high-Z atomic ions which have given rise to some recent interests because of researches of inertial confinement fusion and x-ray laser. Based on the RMCT, the positions and widths of doubly excited sp2n⁺, sp2n^-, and 2pnd ¹P₁ resonances are calculated, which are in agreement with the recent experimental measurements. It sets up a sound foundation on which the RMCT should be applicable to high Z atomic ions.