Studies on Short-Lived Molecular Species by Raman Spectroscopy

进行了两方面的研究，取得了以下成果。(1)体内和体外类胡萝卜素激发电子态的皮秒时间分辨共振拉曼散射.激发单线态（2^1 Ag），激发三线态（^3 Bu），和Chromatium vinosum色素细胞中类胡萝卜素的基态（^1Ag）电子态（主要是类黄质和视紫红质）和相同的类胡萝卜素在苯溶液中的皮秒时间分辨共振拉曼散射检查。对体外和体内类胡萝卜素的2^1 Ag和^1 Ag共振拉曼谱带随时间变化的强度的比较表明，^1 Ag中的振动激发能级直接由2^1 Ag态的衰变填充，并且这些能级在<50 ps内弛豫成热化分布。非对称展宽的基态共振拉曼带的出现支持了这一结论。^3Bu状态的形成 ...更多信息 在色素体中的类胡萝卜素中观察到了te，但在体外的三色堇黄质中没有观察到te，这表明^3Bu态是由色素体中色素的空间组织产生的裂变过程形成的。(2)体内和体外类胡萝卜素的振动弛豫：利用皮秒时间分辨反斯托克斯共振拉曼光谱，定量表征了光合细菌色素-蛋白质复合物中类胡萝卜素（体内）和大豆黄素（体外）在苯和甲苯溶液中种群动力学中的基态^1 Ag振动弛豫。对于体外样品，反斯托克斯共振拉曼信号在<approximately equal>光激发后10 ps达到最大值，然后以15 ps的速率衰减<approximately equal>到反映热化^1 Ag振动布居数的强度。对于体内情况，最大带强度在<approximately equal>由567 nm泵浦（6 ps FWHM）和576 nm探测（6 ps FWHM）激光脉冲定义的互相关时间（8 ps）内发现，而衰减速率与体外样品相似。

Two lines of research have been pursued, and the following results have been obtained.(1) Picosecond time-resolved resonance Raman scattering from excited electronic states of carotenoids in vivo and in vitro.The vibrational spectroscopy and population dynamics of excited singlet (2^1Ag), excited triplet (^3Bu), and the ground (^1Ag) electronic states of carotenoids in chromatophores of Chromatium vinosum (mainly spirilloxanthin and rhodopin) and of the same carotenoids in benzene solutions are examined by picosecond time-resolved resonance Raman scattering. Compariosons of the time-dependent intensities of 2^1Ag and ^1Ag resonance Raman bands from both in vitro and in vivo carotenoids suggest that vibrationally-excited livels in ^1Ag are populated directly by the decay of the 2^1Ag state and that these levels relax into a thermalized distribution in <50 ps. The appearance of asymmetrically broadened ground-state resonance Raman bands supports this conclusion. Formation of the ^3Bu sta … More te is observed for carotenoids in chromatophores, but not for in vitro spirilloxanthin indicating that the ^3Bu state is formed by fission processes originating from the spatial organization of pigments within chromatophores.(2) Vibrational Relaxation in Carotenoids in Vivo and in Vitro.The ground-state ^1Ag vibrational relaxation in the population dynamics of carotenoids in pigment-protein complexes of photosynthetic bacteria (in vivo) and of spirilloxanthin in benzene and toluene solutions (in vitro) is quantitatively characterized using picosecond time-resolved anti-Stokes resonance Raman spectroscopy. For in vitro samples, anti-stokes resonance Raman signals reach maxima <approximately equal>10 ps after optical excitation before decaying with a rate of <approximately equal>15 ps to intensities which reflect a thermalized ^1Ag vibrational population. For the in vivo case, the maximum band intensities are found within the cross-correlation time (<approximately equal>8 ps) defined by the 567 nm pump (6 ps FWHM) and 576 nm probe (6 ps FWHM) laser pulses while the decay rate is similar to that of the in vitro samp Less