Electronic coherence provides a direct proof for energy-level crossing in photoexcited lutein and beta-carotene.
We investigate femtosecond transient absorption dynamics of lutein and beta-carotene. Strong oscillations up to about 400 fs are observed, depending on excitation or detection wavelength and solvent. We propose electronic quantum beats as the origin of these oscillations. They provide direct proof for strong coupling of the 1B(u)(+) with another electronic "dark" state predicted by quantum chemical calculations to be the 1B(u)(-) state resulting in a crossing within a dynamic relaxation model. The overall dynamics can be described well by an optical Bloch equation approach.
Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany.
Evgeny
E
Ostroumov
Marc G
MG
Müller
Christel M
CM
Marian
Martin
M
Kleinschmidt
Alfred R
AR
Holzwarth
D014975:Lutein / Q000737:chemistry*; D008956:Models, Chemical; D055668:Photochemical Processes; D011789:Quantum Theory; D013816:Thermodynamics; D019207:beta Carotene / Q000737:chemistry*
D019207:beta Carotene; D014975:Lutein