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首页> 外文期刊>Applied Magnetic Resonance >Two-laser two-color time-resolved EPR study on higher-excited-state triplet-singlet intersystem crossing of porphyrins and phthalocyanines
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Two-laser two-color time-resolved EPR study on higher-excited-state triplet-singlet intersystem crossing of porphyrins and phthalocyanines

机译：卟啉和酞菁的高激发态三重态-单重体系间相交的两色双色时间分辨EPR研究

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摘要

Photoinduced effects on the electron spin polarization (ESP) in the lowest excited triplet (T-l) states of porphyrins (PORs) and phthalocyanines (PCs) have been observed with a two-color time-resolved (TR) electron paramagnetic resonance (EPR) technique in a glassy matrix at low temperatures. On single-color excitation with the wavelengths of the ground state absorptions of PORs and PCs, polarized EPR spectra due to the corresponding T-l state were observed. The polarization patterns match well with interpretation as anisotropic intersystem crossing (ISC) induced by the spin-orbit coupling between the singlet excited (S-l) and the triplet states. In contrast, two-color excitation led to a change of the phase of the T-l state polarization pattern to the opposite. The observed ESP in the T-l state resulting from the excitation to the upper triplet state (T-n) was interpreted in terms of anisotropic ISC between the T-n and S-l states. From the analysis of the ESP, changes in the quantum yields of the reverse ISC processes were determined at different temperatures. The results could be best interpreted by the existence of thermal pathways with small activation energy in the relaxation processes. [References: 21]
机译：用双色时间分辨（TR）电子顺磁共振（EPR）技术观察到了卟啉（POR）和酞菁（PC）在最低激发三重态（Tl）状态下对电子自旋极化（ESP）的光诱导效应。在低温下呈玻璃状基质。在具有POR和PC的基态吸收波长的单色激发下，观察到由于相应的T-1状态引起的偏振EPR光谱。极化模式与单线激发态（S-1）和三线态之间的自旋轨道耦合引起的各向异性系统间交叉（ISC）的解释非常吻合。相反，双色激发导致T-1状态偏振图案的相位相反变化。根据在T-n和S-1状态之间的各向异性ISC来解释由激发到上部三重态（T-n）导致的在T-1状态下观察到的ESP。通过对ESP的分析，确定了在不同温度下反向ISC过程的量子产率的变化。弛豫过程中活化能较小的热通道的存在可能是最好的解释结果。 [参考：21]

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