Absorption spectra for a model light-harvesting system using non-Markovian theories

Different theories for the determination of the linear absorption are compared. As a test system we used a simplified B850 ring of bacteriochlorophylls within a light-harvesting complex of purple bacteria. Starting with a quantum master equation, the frequency-domain absorption spectra can be calculated within linear response. In these quantum master equations one often decouples the population dynamics from that of the coherences (secular approximation) and neglects memory effects (Markov approximation). The absorption spectra of the ring aggregate resulting from the Redfield theory with and without secular approximation are compared to those results from a time-local and a time-non-local non-Markovian theory.