Tunnelling in asymmetric double-well potentials: varying initial states

Tunnelling in a double-well potential has features which are not derivable through a mere extension of the concepts used in the context of a single potential barrier with no con fining walls on either side. Furthermore, an asymmetric double-well potential, relevant in many contemporary areas of physics and chemistry, possesses certain distinctive aspects in contrast to the relatively simple case of a symmetric double-well potential. In this paper a self-contained numerical and analytical study of these features is reported, and a theoretical model is presented with special attention being given to a unified treatment of both the symmetric and asymmetric cases. The popularly used pair-state model is critically examined, and the important role of the initial state (which is rarely discussed in the literature) is highlighted with specific examples. (C) 2001 Academic Press.