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.
Phys Chem Chem Phys. 2013 Dec 14;15(46):20026-36. doi: 10.1039/c3cp53323a.
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.
类胡萝卜素激发态动力学的研究引起了人们的极大兴趣，由于瞬态物种的光谱峰强烈重叠和复杂的动力学，产生了许多有争议的假设。在本工作中，为了更好地理解类胡萝卜素激发态过程的复杂性，我们采用飞秒泵浦-探针光谱法研究了乙醇中全反式β-胡萝卜素的激发态动力学。在β-胡萝卜素的强允许 S2 态激发后，在可见光谱范围内记录了瞬态吸收光谱。为了进行比较，在选定的波长处，通过多指数函数拟合动力学轨迹，对时间分辨瞬态吸收光谱进行了传统分析，然后再次通过软建模多元曲线分辨交替最小二乘分析（MCR-ALS）方法对纯谱进行建模，并通过广义二维（2D）相关光谱数据分析为光谱特征动力学提供附加信息。MCR-ALS 分析表明，使用二维相关光谱识别的 S态动力学和 S1 态动力学的发展与振动热 S1v'态的弛豫不同。结果表明，热 S1v'和 S态具有不同的相关差异光谱。我们分析的结果表明，在这项工作中观察到的 S*态不是热 S1v'态，而是一个单独的单线态。
