The Rotational Spectrum of Tunnelling Methyl Groups

The quantum-classical transition of methyl rotation highlights conflicting assumptions of quan­ tum and classical mechanics, the first assuming that identical fermions are indistinguishable while the second recognises they are distinguishable through their histories. When this is introduced into quantum mechanics, the two are compatible and there is a smooth transition of the methyl rotational spectrum with increasing temperature through the merger of three broadening peaks. The changing character of methyl dynamics through this transition is discussed.