Figure 2.

Pictorial depiction of the transitions giving rise to the Kβ mainlines. In brief, 1s ionization from a totally symmetric ⁶S ground state (1s²3p⁶3d⁵) gives rise to ⁷S and ⁵S intermediate states (1s¹3p⁶3d⁵) that are split only by the small 1s–3d exchange and, thus, are nearly degenerate. Enumerating the possible final states in the absence of spin orbit coupling, one ⁷P and three ⁵P final states (1s²3p⁵3d⁵) are accessible; the parent 3d⁵ terms are shown in parentheses. The intensity of the formally allowed transition to the (⁴P)⁵P state is calculated to be very small and does not contribute significantly to the spectral shape.