The radiative corrections of order α
3
rydbergs are evaluated for the ionization energy of the metastable states 2
1
,
3
S, of the helium atom. In the calculation of the average excitation energy
k
0
, the main contribution comes from the transition to and (
ms, np
) and (
ms, ∊p
) states. The oscillator strengths for transitions to (1
s, ∊p
), (2
s, ∊p
) and (3
s, ∊p
) states are evaluated by using six-parameter wavefunction for the metastable states and a product of a hydrogenic wavefunction with
Z
= 2 for the
s
electron and a wavefunction analogous to the Hartree wavefunction for the excited
p
electron. Making use of these oscillator strengths and a method used by Pekeris, the values of the average excitation energies for the singlet and triplet states are found to be 77.09 ± 1.6 and 79.84 ± 1.0 rydbergs respectively. With these values of the average excitation energies, the Lamb shift corrections, including the estimate of a α
4
Ry order corrections, to the ionization energies of the singlet and triplet states become – 0.106 ± 0.018 cm
-1
and –0.129 ± 0.013 cm
–1
respectively. When they are added to the theoretical values of the ionization energies obtained by Pekeris, the values of the ionization energies become 32033.212 ± 0.018 an d 38454.698 ± 0.013 cm
-1
compared with Herzberg’s experimental values of 32033.24 ± 0.05 an d 38454.73 ± 0.05 cm
-1
for the singlet and triplet states respectively.
How do the Hückel and Baird Rules Fade away in Annulenes?