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On the definition of nonadiabatic effects in curve‐crossing problems
Author(s) -
Broeckhove J.,
Keutgens W.,
Lathouwers L.,
Van Leuven P.
Publication year - 1995
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560550103
Subject(s) - adiabatic process , adiabatic theorem , eigenvalues and eigenvectors , adiabatic quantum computation , level crossing , physics , avoided crossing , quantum mechanics , born–huang approximation , exact solutions in general relativity , quantum , mathematics , mathematical analysis , excited state , approximation error , quantum computer , archaeology , history
When two electronic potentials present an avoided crossing, the adiabatic approximation breaks down in the energy region near to the crossing. In particular, the correspondence between exact energy levels of the two‐state system and the adiabatic levels of the lower and upper adiabatic potentials becomes ambiguous. This implies that the term “nonadiabatic effect,” used for the difference between exact and adiabatic energy eigenvalues, loses its meaning in the crossing regime unless an unambiguous way of assigning an adiabatic to an exact level is defined. This is important in order to investigate where nonadiabatic schemes, such as the generator coordinate approximation, fit in between the adiabatic approximation and quasi‐exact approaches. © 1995 John Wiley & Sons, Inc.