Calculations of double-excited states in He, N⁵⁺and N³⁺using B-splines

The authors report calculations of energies and wavefunctions for doubly-excited states using a direct diagonalization method in a B-spline basis. They report results for bound 1 S e and 1 P 0 states in He and quasi-bound 3lnl' states in N 5+ and N 3+ . The latter case has a 1s 2 core and they show that the B-spline technique can easily be extended to quasi-bound states outside a closed core. They show that the B-spline approach in this case can compete with the most accurate techniques available. Also the influence of the core on the composition of the 3l3l' states is studied.