LONG RANGE-DIPOLE ADAPTED BASIS FOR DOUBLY-EXCITED STATES

We analyse the use of dipole adapted basis (DAB) functions to calculate energy positions and widths of doubly excited states of H- and He. By using DAB functions, classification of doubly excited states follows from simply diagonalizing the Hamiltonian for each channel separately. Our results for H- show that both energies and widths obtained with DAB functions are in good agreement with results of accurate calculations, thus showing that the physics of doubly excited states in H- is essentially controlled by the long range dipole interaction. On the other hand, the model does not work to describe autoionization lifetimes in He, even qualitatively.