Scientific Results

Identification of the excited-state C=C and C=O modes of trans -ß-apo-8

Year: 2015

Authors: Di Donato M., Ragnoni E., Lapini A., Kardas¨ T.M., Ratajska-Gadomska B., Foggi P., Righini R.

Autors Affiliation: LENS (European Laboratory for Non Linear Spectroscopy), via N. Carrara 1, Sesto Fiorentino, 50019, Italy; INO (Istituto Nazionale di Ottica), Largo Fermi 6, Firenze, 50125, Italy; Dipartimento di Chimica ugo Schiff, Università di Firenze, via della Lastruccia 13, Sesto Fiorentino, 50019, Italy; Department of Chemistry, University of Warsaw, Zwirki Wigury 101, Warsaw, 02-089, Poland; Dipartimento di Chimica, Università di Perugia, via Elce di Sotto 8, Perugia, 06100, Italy; Institute of Experimental Physics, Department of Physics, University of Warsaw, Pasteura 5, Warsaw, 02-093, Poland

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-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-ß-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.

Journal/Review: THE JOURNAL OF PHYSICAL CHEMISTRY LETTERS

Volume: 6 (9)      Pages from: 1592  to: 1598

More Information: We gratefully acknowledge support from the Italian MIUR: project PRIN-2010ERFKXL-004 and program FIRB “Futuro in Ricerca 2010” grant RBFR10Y5VW to M.D.D. and RBFR109ZHQ supporting A.L. and project EFOR-CABIR L. 191/2009 art. 2 comma 44 and funding from LASERLAB-EUROPE (grant agreement no. 284464, EC’s Seventh Framework Programme).
KeyWords: Charge transfer; Infrared spectroscopy; Molecules; Pigments; Quantum chemistry; Quantum theory; Raman spectroscopy; Spectroscopic analysis, carotenoids; Electronic excited state; Femtosecond stimulated raman spectroscopies; Nonlinear spectroscopic techniques; photodynamics; Quantum chemical calculations; Raman; vibrations, Excited states
DOI: 10.1021/acs.jpclett.5b00528

Citations: 6
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