STUDIES OF DOUBLY EXCITED STATES AND PHOTODETACHMENT IN NEGATIVE IONS E. Lindroth and N. Brandefelt Department of Atomic Physics, Stockholm University, Frescativ. 24, S-104 05 Stockholm, Sweden We present a new ab initio approach to three-electron systems. Complex rotation combined with $B$-spline basis functions are used to construct and diagonalize the three-particle matrix. All three electrons are treated on equal footing. The method has been applied to 4^S -symmetry states of He- above the single ionization threshold, the same region where accurate experiments are available. Several resonances observed in the experiments, but previously not calculated, have been found.