Double Excitation of Light Atoms by Electron Impact.

A theory of light atoms is developed in such a way that one can see systematically how one goes from close -coupling to distorted-wave and finally to Born-Oppenheimer. The explicit close-coupling equations for two-electron type atoms are derived and a computer program for their solutions is developed. These equations are solved to obtain distorted wave solutions for the parity favored double excitation of the ('3)P(,g) state of helium from threshold to 110 eV.