Identification of the Excited-State C═C and C═O Modes of trans-β-Apo-8'-carotenal with Transient 2D-IR-EXSY and Femtosecond Stimulated Raman Spectroscopy.
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-IR-EXSY) and femtosecond stimulated Raman spectroscopy (FSRS), the contribution of the C═C and C═O 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.
†LENS (European Laboratory for Non Linear Spectroscopy), via N. Carrara 1, 50019 Sesto Fiorentino, Italy.|‡INO (Istituto Nazionale di Ottica), Largo Fermi 6, 50125 Firenze, Italy.|§Dipartimento di Chimica "Ugo Schiff", Università di Firenze, via della Lastruccia 13, 50019 Sesto Fiorentino, Italy.
Mariangela
M
Di Donato
†LENS (European Laboratory for Non Linear Spectroscopy), via N. Carrara 1, 50019 Sesto Fiorentino, Italy.|‡INO (Istituto Nazionale di Ottica), Largo Fermi 6, 50125 Firenze, Italy.
Elena
E
Ragnoni
†LENS (European Laboratory for Non Linear Spectroscopy), via N. Carrara 1, 50019 Sesto Fiorentino, Italy.|‡INO (Istituto Nazionale di Ottica), Largo Fermi 6, 50125 Firenze, Italy.|§Dipartimento di Chimica "Ugo Schiff", Università di Firenze, via della Lastruccia 13, 50019 Sesto Fiorentino, Italy.
Andrea
A
Lapini
∥Department of Chemistry, University of Warsaw, Zwirki Wigury 101, 02-089 Warsaw, Poland.
Tomasz M
TM
Kardaś
∥Department of Chemistry, University of Warsaw, Zwirki Wigury 101, 02-089 Warsaw, Poland.
Boźena
B
Ratajska-Gadomska
†LENS (European Laboratory for Non Linear Spectroscopy), via N. Carrara 1, 50019 Sesto Fiorentino, Italy.|‡INO (Istituto Nazionale di Ottica), Largo Fermi 6, 50125 Firenze, Italy.|⊥Dipartimento di Chimica, Università di Perugia, via Elce di Sotto 8, 06100 Perugia, Italy.
Paolo
P
Foggi
†LENS (European Laboratory for Non Linear Spectroscopy), via N. Carrara 1, 50019 Sesto Fiorentino, Italy.|‡INO (Istituto Nazionale di Ottica), Largo Fermi 6, 50125 Firenze, Italy.|§Dipartimento di Chimica "Ugo Schiff", Università di Firenze, via della Lastruccia 13, 50019 Sesto Fiorentino, Italy.
Roberto
R
Righini
Raman; T2D-IR; carotenoids; charge transfer; photodynamics; vibrations