Coherent High-Frequency Vibrational Dynamics in the Excited Electronic State of All-Trans Retinal Derivatives
2015-12-16T22:23:23Z (GMT) by
Coherent vibrational dynamics of retinal in excited electronic states are of primary importance in the understanding of photobiology. Using pump-DFWM, we demonstrate for the first time the existence of coherent double-bond high-frequency modulations (>1300 cm–1) in the excited electronic state of different retinal derivatives. All-trans retinal as well as retinal Schiff bases exhibit a partial frequency downshift of the CC double-bond mode from ∼1580 cm–1 in the ground state to 1510 cm–1 in the excited state. In addition, a new vibrational band at ∼1700 cm–1 assigned to the CN stretching mode in retinal Schiff bases in the excited state is detected. The newly reported bands are observed only in specific spectral regions of excited-state absorption. Implications regarding the observation of vibrational coherences in naturally occurring retinal protonated Schiff bases in rhodopsins are discussed.