Room temperature absorption and emission spectra of the all-trans isomers of decatetraene, dodecapentaene, tetradecahexaene, and hexadecaheptaene have been obtained in a series of nonpolar solvents. The resolved vibronic features in the optical spectra of these model systems allow the accurate determination of S0 (11Ag-) → S2 (11Bu+) and S1 (21Ag–) → S0 (11Ag–) electronic origins as a function of solvent polarizability. These data can be extrapolated to predict the transition energies in the absence of solvent perturbations. The effects of the terminal methyl substituents on the transition energies also can be estimated. Franck–Condon maxima in the absorption and emission spectra were used to estimate differences between S0 (11Ag–) → S1 (21Ag–) and S0 (11Ag–) → S2 (11Bu+) electronic origins and “vertical” transition energies. Experimental estimates of the vertical transition energies of unsubstituted, all-trans polyenes in vacuum as a function of conjugation length are compared with long-standing multireference configuration interaction (MRCI) treatments and with more recent ab initio calculations of the energies of the 21Ag– (S2) and 11Bu+ (S2) states.
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机译：在一系列非极性溶剂中，获得了十邻苯三烯，十二碳五烯，十四碳六烯和十六碳六烯的全反式异构体的室温吸收和发射光谱。这些模型系统的光谱中解析出的振动特征可以准确确定S0（1 1 Ag -）→S2（1 1 Bu + ）和S1（2 1 Ag – ）→S0（1 1 Ag – < / sup>）电子起源是溶剂极化率的函数。可以外推这些数据以预测在没有溶剂干扰的情况下的跃迁能。还可以估计末端甲基取代基对跃迁能的影响。利用吸收和发射光谱中的弗兰克-康登极大值来估计S0（1 1 Ag – ）→S1（2 1 Ag之间的差异 – ）和S0（1 1 Ag – ）→S2（1 1 Bu + ）电子起源和“垂直”跃迁能量。实验中将未取代的全反式多烯在真空中的垂直跃迁能作为共轭长度的函数进行了实验估算，并将其与长期使用的多参比组态相互作用（MRCI）处理以及最近的从头算起的2 1 A g – （S 2 ）和1 1 B u < / sub> + （S 2 ）状态。
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