True minimum tunneling

When the central barrier in a double energy minimum decreases below the lowest zero point vibrational level, the situation is equivalent to a true single minimum case (Forsen et al., 1978). A carbon tunnelling mechanism suggested to explain the dynamic behaviour in 2-norbornyl cations, (Fong, 1974 Dewar and Merz, 1986) has been shown to be unimportant (Yannoni etaL 1985). 

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