Singly excited helium state
= Singly excited helium state
A bound-state configuration with one <electron> predominantly in $1s$ and the other in a different orbital $n\ell$. The two assignments of identical <electrons> to these orbitals must be combined with the appropriate <exchange symmetry of two identical spin-one-half fermions>. Symmetric spatial combinations accompany the <singlet state>; antisymmetric combinations accompany the <triplet state>.