Fucoxanthin, a typical carotenoid that absorbs in the blue end of visible light, whose detailed electronic structures remain to be clarified. It is well known that carotenoids harvest energy from sunlight and transfer it to chlorophylls (Chls) and/or bacteriochlorophylls (BChls) through its excited states as the intermediate states, however, some excited states still need evidence to be definitely confirmed. Through steady-state fluorescence emission spectroscopy and femtosecond time-resolved fluorescence up-conversion technique, we provide new evidence for the identification of the excited Sx state in fucoxanthin, a representative of carotenoids. The fluorescence emission from the intramolecular charge transfer (ICT) states was also observed and identified for first time according to our limited survey. Our findings suggest that fucoxanthin absorbs the blue light and transfer most of energy to BChls via S_x and ICT1 states for certain bacteria, but release them via ICT1 state to protect aginst light damage for algea.

中文翻译：

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岩藻黄质中分子内电荷转移态的 Sx 态和荧光发射的实验证据


岩藻黄质，一种典型的类胡萝卜素，吸收可见光的蓝色端，其详细的电子结构仍有待阐明。众所周知，类胡萝卜素从阳光中收集能量，并通过其激发态作为中间态将其转移到叶绿素 （Chls） 和/或细菌叶绿素 （BChls），但是，一些激发态仍然需要证据来明确确认。通过稳态荧光发射光谱和飞秒时间分辨荧光上转换技术，我们为鉴定类胡萝卜素的代表岩藻黄质中激发的 Sx 态提供了新的证据。根据我们的有限调查，还首次观察到并鉴定了分子内电荷转移 （ICT） 状态的荧光发射。我们的研究结果表明，岩藻黄质吸收蓝光并通过某些细菌的 S_x 和 ICT1 状态将大部分能量转移到 BChls，但通过 ICT1 状态释放它们以保护藻类的光损伤。