Lda. Siebbeles et al., SIMPLE AND ACCURATE WAVE-FUNCTIONS FOR 2-ELECTRON ATOMS IN S, P AND DSTATES, Journal of physics. B, Atomic molecular and optical physics, 26(13), 1993, pp. 321-325
A simple wavefunction containing two variational parameters is shown t
o yield accurate energies of two-electron atoms. In contrast to previo
us analogous treatments the present method proves not only successful
for S states, but also gives accurate results for P and D states.