Attaching the molecule to one or both of the metalelectrodes changes the situation. Just as atomic orbitalscan be coupled to form molecular orbitals, the molecu-lar states couple to the wavelike states in the metal, thussmearing out the molecular energy levels. Further-more, ignoring thermal effects, the electrons will re-arrange themselves to occupy the lowest availablestates of the whole system, even if that means transfer-ring charge between the molecule and the metal. Align-ment between molecular and metal levels, whichcritically affects tunnelling and therefore conduction,turns out to depend in detail on the metals, the mole-cule and the precise molecule–metal binding.
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