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Title: Absorption lineshapes of molecular aggregates revisited

Linear absorption is the most basic optical spectroscopy technique that provides information about the electronic and vibrational degrees of freedom of molecular systems. In simulations of absorption lineshapes, often diagonal fluctuations are included using the cumulant expansion, and the off-diagonal fluctuations are accounted for either perturbatively, or phenomenologically. The accuracy of these methods is limited and their range of validity is still questionable. In this work, a systematic study of several such methods is presented by comparing the lineshapes with exact results. It is demonstrated that a non-Markovian theory for off-diagonal fluctuations, termed complex time dependent Redfield theory, gives good agreement with exact lineshapes over a wide parameter range. This theory is also computationally efficient. On the other hand, accounting for the off-diagonal fluctuations using the modified Redfield lifetimes was found to be inaccurate.
Authors:
;  [1] ;  [2] ;  [1]
  1. Department of Theoretical Physics, Faculty of Physics, Vilnius University, Sauletekio 9-III, 10222 Vilnius (Lithuania)
  2. (Lithuania)
Publication Date:
OSTI Identifier:
22415658
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 142; Journal Issue: 15; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ABSORPTION; ABSORPTION SPECTROSCOPY; COMPARATIVE EVALUATIONS; DEGREES OF FREEDOM; ELECTRONIC STRUCTURE; FLUCTUATIONS; LIFETIME; MARKOV PROCESS; TIME DEPENDENCE; VIBRATIONAL STATES