Positron attachment to the He(ns^{2 1}S^e) states

Calculations based on the projection method and using explicitly correlated Gaussians are used to confirm the existence of positron attachment to two doubly excited states of helium. The e⁺He(2s^{2 1}Se) and e ⁺He(3s^{2 1}S^e) states have binding energies of 0.449 and 0.286 eV. These estimates of the resonance energies are nearer to the variational limit than previous calculations. These states will exist as resonances in the e ⁺-He scattering continuum, and complex rotation calculations have been used to estimate their widths.