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We point out the advantages of the full quantum-mechanical treatment of the asymmetric coupled double well (~coaw) in an electric field. We believe that a clearer physical picture of resonance tunnelling emerges from this approach than from the approximate m e which treats the ACOQW as a composite of two isolated wells placed in contact. In an electric field energy levels of the first two bound States first approach each other, but do n d cross, and later, with increasing field, their separation again increases. Resonance effects occur at the value of the field at which the ieveis are closest to each other. At the same time the occupation probabilities of the two wells are equal. Funhermore, it is shown that the double well with a thin barrier behaves as coupled even at fields far from resonance. This claim is substantiated by an approximate calculation of the absorption coefficient in the wide well and a WmDarison of the calculated values with experiment (Leo et @.

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