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Fig. 2

image

Term diagram of the Ca II model atom. Atomic levels (horizontal bars) are shown with their valence electron configuration nl to theleft, the total angular momentum J on top (as a fraction), grouped by their term configuration 2S+1LP at the bottom row. Bound-bound permitted (solid lines) and forbidden (dashed lines) transitions connect the levels. PRD transitions are indicated in orange. Bound-free transitions (dotted lines) connect their levels to the Ca II continuum (hashed area). For all transitions, the line center or threshold wavelengths are given in Ångströms.

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