ELECTRON-IMPACT EXCITATION CROSS-SECTIONS OF SODIUM 2P(5)3S(2) P-2 AUTOIONIZING STATE FROM THRESHOLD TO 1.5 KEV

Relative excitation cross sections of the lowest-lying autoionizing st ate 2p(5)3s(2) P-2 Of sodium are measured for electron impact in the r ange of incident energy E-0 from 1.5 keV down to the threshold. Absolu te cross sections are obtained by normalization of the relative cross sections at E-0 = 1.5 keV to the theoretical cross section in the plan e-wave Born approximation with accurate atomic wavefunctions. Negative ion resonances near the excitation threshold are observed and reprodu ced by a 26-state R-matrix calculation. The cross sections at intermed iate incident energies are obtained in the distorted-wave Born approxi mation and are compared with the present experimental values and with theoretical values of other authors.