4s-Orbitals in sulphur

Abstract

Energies of the spectral terms arising from electron configurations s²p³4s, as well as those of valence states 3(s²p³)⁺, 3(sp⁴)⁺, 4(s²p³4s), 5(sp³4s)⁺, 5(sp³d)⁺, and 6(sp³d4s) of sulphur have been evaluated with an orthonormal set of Slater functions. The occupation of a 4s orbital is always favoured (ca. 2 eV) over that of a 3d orbital. The mean radius of the 4s orbital for the electron configurations investigated is fairly constant (about 3 Å). In 6(sp³d4s) and 5(sp³d)⁺ the mean radius of the 3d orbital is of the order of magnitude of a sulphur–carbon bonding distance. The reliability of the analytical function chosen to represent the 4s orbital is discussed. The point-charge approximation to the potential field in which the 4s electron moves is shown to be rather inaccurate. The importance of core–valence intratomic exchange terms is assessed.