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The low‐lying excitation energies of polyenes investigated with a chain‐length‐dependent screened potential
Author(s) -
Siregar R. E.,
Tjia M. O.
Publication year - 1993
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.560480408
Subject(s) - polyene , excited state , excitation , chemistry , configuration interaction , parametrization (atmospheric modeling) , chain (unit) , atomic physics , factorization , molecular physics , physics , computational chemistry , quantum mechanics , mathematics , algorithm , organic chemistry , radiative transfer
The chain‐length dependencies of 2Ag and 1Bu excitation energies as well as their unexpected inversion observed experimentally in trans ‐polyenes have so far been explained satisfactorily only in terms of configuration interactions within the standard Pariser–Parr–Pople ( PPP ) parametrization scheme with at least double excitations involving prohibitively large computational labor for long polyenes. A simpler calculation allowing nonzero differential overlap and employing restricted (first‐order) single‐excitation configuration interaction with chain‐length‐dependent screened potential is shown to provide an adequate alternative for the studies of those basic spectroscopic features of polyene excited states. The screening factor is parametrized in accordance with the chain‐length‐dependent behavior of the electrical polarizabilities of polyenes derived within the standard PPP approximation scheme. © 1993 John Wiley & Sons, Inc.