title: Excited state dynamics of β-carotene studied by means of transient absorption spectroscopy and multivariate curve resolution alternating least-squares analysis.
abstract: Determination of the excited-state dynamics of carotenoids has attracted considerable interest, engendering a number of controversial hypotheses because of the strongly overlapping spectral peaks and complicated dynamics of transient species. In the present work, aiming for better understanding the complexity of excited-state processes in carotenoids, excited-state dynamics of all-trans-β-carotene in ethanol was investigated by femtosecond pump-probe spectroscopy. Following the excitation of the strongly allowed S2 state of the β-carotene, transient absorption spectra were recorded in the visible spectral range. For comparison, the time-resolved transient absorption spectra are analyzed in a conventional way, fitting kinetic traces with a multi-exponential function at chosen wavelengths from obtained spectra, and then again by means of the soft-modeling multivariate curve resolution alternating least-squares analysis (MCR-ALS) method for modeling pure profiles and the generalized two-dimensional (2D) correlation spectroscopy data analysis for providing additional information on the dynamics of spectral features. MCR-ALS analysis shows that both the dynamics of the S* state, identified using the 2D correlation spectra, and the S1 state develop on a different timescale than the relaxation of the vibrationally hot S1v' state. Hot S1v' and S* states are shown to have different species associated difference spectra. Results of our analysis indicate that the S* state observed in this work is not the hot S1v' state but instead a separate singlet state.
authors.affiliation: The State Key Laboratory of Molecular Reaction Dynamics and Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing-100190, P. R. China. andong@iccas.ac.cn guoqj@iccas.ac.cn.
authors.forename: Silvije
authors.initials: S
authors.lastname: Vdović
authors.forename: Yingying
authors.initials: Y
authors.lastname: Wang
authors.forename: Boxuan
authors.initials: B
authors.lastname: Li
authors.forename: Meng
authors.initials: M
authors.lastname: Qiu
authors.forename: Xuefei
authors.initials: X
authors.lastname: Wang
authors.forename: Qianjin
authors.initials: Q
authors.lastname: Guo
authors.forename: Andong
authors.initials: A
authors.lastname: Xia
mesh_terms: D000431:Ethanol / Q000737:chemistry; D007536:Isomerism; D016018:Least-Squares Analysis; D008956:Models, Chemical; D013053:Spectrophotometry; D013997:Time Factors; D019207:beta Carotene / Q000737:chemistry*
chemical_list: D019207:beta Carotene; D000431:Ethanol