The autoionisation widths of He I below the N=3 He+threshold

Abstract

The saddle-point technique is extended to calculate autoionisation energies and widths of helium below the n=2 and the n=3 hydrogenic thresholds. The width of the lowest ¹P^o state below the n=3 threshold is determined to be 114.2 meV, but the experimental value of Dhez and Ederer (1973) is (132+or-14) meV. The width of the lowest ¹P^o state below the n=2 threshold is 0.0366 eV, which agrees with the experimental value of 0.0384+or-0.004 eV given by Madden and Codling (1965).