Also associated researcher at CNRS UMR 8112 - LERMA, Observatoire de Paris, Section de Meudon, 92195 Meudon, France.

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For more details, a description of the quantum close coupling method for limiting cases where the diatomic molecule collides with structureless rare gases can be found in Arthurs & Dalgarno (1960), and a general case where the perturbers have arbitrary angular momentum is in Launay (1977).

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... rules

We note however that for collisions involving homonuclear diatomic molecules (C₂, O₂, H₂, ...), only the L-even terms are nonvanishing in the Legendre expansion of the interaction potential. As J+J'+L is of even parity, collisional transitions between even and odd J-levels are forbidden.

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