RAMAN STUDIES OF PHOTOCHEMICAL-REACTIONS IN FULLERENE FILMS
RAMAN STUDIES OF PHOTOCHEMICAL-REACTIONS IN FULLERENE FILMS
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DOI：
10.1016/0009-2614(93)89342-f
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发表时间：
1993-09-10
影响因子：
2.8
通讯作者：
ROTH, S
中科院分区：
文献类型：
--
作者：
AKSELROD, L;BYRNE, HJ;ROTH, S
采用拉曼光谱作为C60无氧和含氧薄膜的结构探针。初始光谱的比较表明，氧包合物对拉曼频率没有影响。然而，观察到峰的振幅对光照敏感。最初观察到的每个峰在几十秒的时间尺度上衰减，而新的峰在低能侧出现大约10个波数。在氧化膜中，降解过程明显较慢。该过程使用一个简单的能级速率方程模型进行分析，在该模型中，三重态的分布导致样品退化，其特征时间为tau2，与基态恢复竞争，其特征为三重态寿命tau1。无氧薄膜中所有拉曼峰的衰减都符合该模型，tau2和tau1的衰减值分别为80 +/- 5 s和55 +/- 5 ms。与降解产物相对应的新光谱特征的上升也符合该模型。在氧化膜中，发现了相似的tau2值，最佳匹配产生的三重态寿命为30 +/- 5 ms。提出氧的作用是通过三重态猝灭抑制光化学降解。
Raman spectroscopy is employed as a structural probe of both oxygen-free and oxygenated thin films of C60. Comparison of initial spectra reveals no influence of oxygen inclusion on the Raman frequencies. The amplitudes of the peaks are, however, observed to be sensitive to light exposure. Each of the initially observed peaks degrades on a time scale of tens of seconds while new peaks emerge approximately ten wavenumbers to the low-energy side. In oxygenated films the degradation process is apparently slower. The process is analyzed using a simple rate equation model of a level scheme in which population of the triplet state leads to a sample degradation with a characteristic time tau2, competing with the ground state recovery, characterized by the triplet lifetime, tau1. The decay of all the Raman peaks in oxygen-free films fits well to such a model with values of 80 +/- 5 s and 55 +/- 5 ms for tau2 and tau1, respectively. The rise of the new spectral features, corresponding to the degraded product, also fits the model. In oxygenated films, where a similar value of tau2 is found, the best fits yield a triplet lifetime of 30 +/- 5 ms. It is proposed that the role of oxygen is to inhibit the photochemical degradation via triplet quenching.