EXCITATION OF THE 2(3)S METASTABLE STATE OF HELIUM BY ELECTRONS

A systematic calculation for the total and differential cross sections for electron impact excitation of helium from its initially excited m etastable 2(3)S state to higher states namely n(1.3)S and n(1.3)P (wit h n=2-4) states is reported. Distorted wave approximation theory has b een used for the calculation. The effect of different distortion poten tials as well as the effect of target polarization by the projectile i s explicitly considered. For comparison similar first Born level resul ts are also calculated. Results are compared with the available earlie r calculations and experimental data.