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These latter two types of molecules are of interest for the spectroscopy as well as for the dynamics communities, because of the nearly degenerate doublets (l-type or Λ type doubling), which are attributed to either vibrational or electronic contribution on the internuclear projection of total angular momentum J. 

lタイプ：振動準位が縮退していることで、状態が2つあること。

λタイプ：電子準位が縮退していることで、状態が2つあること。