Assigning the vibrational modes of molecules in the electronic excited state is often a difficult task. Here we show that combining two nonlinear spectroscopic techniques, transient 2D exchange infrared spectroscopy (T2D-IREXSY) and femtosecond stimulated Raman spectroscopy (FSRS), the contribution of the CC and CO modes in the excited-state vibrational spectra of trans-β-apo-8′- carotenal can be unambiguously identified. The experimental results reported in this work confirm a previously proposed assignment based on quantum-chemical calculations and further strengthen the role of an excited state with charge-transfer character in the relaxation pathway of carbonyl carotenoids. On a more general ground, our results highlight the potentiality of nonlinear spectroscopic methods based on the combined use of visible and infrared pulses to correlate structural and electronic changes in photoexcited molecules.
Identification of the Excited-State C═C and C═O Modes oftrans-β-Apo-8′-carotenal with Transient 2D-IR-EXSY and Femtosecond Stimulated Raman Spectroscopy
FOGGI, Paolo;
2015
Abstract
Assigning the vibrational modes of molecules in the electronic excited state is often a difficult task. Here we show that combining two nonlinear spectroscopic techniques, transient 2D exchange infrared spectroscopy (T2D-IREXSY) and femtosecond stimulated Raman spectroscopy (FSRS), the contribution of the CC and CO modes in the excited-state vibrational spectra of trans-β-apo-8′- carotenal can be unambiguously identified. The experimental results reported in this work confirm a previously proposed assignment based on quantum-chemical calculations and further strengthen the role of an excited state with charge-transfer character in the relaxation pathway of carbonyl carotenoids. On a more general ground, our results highlight the potentiality of nonlinear spectroscopic methods based on the combined use of visible and infrared pulses to correlate structural and electronic changes in photoexcited molecules.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
