Transition element complexes energy-level diagrams

While the energy level diagrams and the corresponding spectroscopic transitions are relatively straightforward for light elements, they become very complex for heavier elements. The number of observed Hnes listed by Harvey [3] increases from the alkah metals with 30 (for lithium) to 645 (for caesium) to several thousand lines for the transition elements (chromium 2277, iron 4757, and cerium 5755 lines, respectively). 

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