Qualitative feature of the low-lying spectrum of intrashell states of 4-valence-electron atoms derived from symmetry consideration

Inherent nodal surfaces existing in the wavefunctions of intrashell states of 4-valence-electron atoms have been investigated. The decisive effect of these surfaces has been demonstrated, the ordering of low-lying levels has been predicted, a primary classification scheme has been proposed, the existence of three rotation bands has been suggested.