A calculation of the binding energy of excited states of an electron bound to a substitutional +2e point charge in Si is presented. Direct and umklapp intervalley interactions are included. Very large valley-orbit splittings for 1s and 2s levels are obtained, whereas p-like and ns levels (n>or=3) are well described by one-valley effective-mass theory. The spectrum is in fair agreement with recent experiments on chalcogen donors.
 

Physica B & C, 117-118 B + C 122-4, 1983.