Triplet States Studied by Two-Color Excitation Time-Resolved ESR

在本研究项目中，我们使用时间分辨ESR技术进行了四个项目。所得结果总结如下。(1)向高三重态的能量转移：用常规的光谱学很难知道在三重态-三重态能量转移过程中产生了什么样的能量受体三重态。然而，我们成功地通过时间分辨ESR确定了能量转移到更高的三重态（T_2），并确定了T_2能量。(2)三重-双重体系中的自旋极化转移：利用相对稳定的自由基作为双重源，研究了三重-双重体系中自旋极化转移的机理。由于自旋极化转移发生在三重态能量高于自由基激发能时，故为。得出自旋极化转移伴随着能量转移的结论。(3)苄基和α -萘酚的自旋极化倒转：苄基和α -萘酚与苯胺和苯酚反应产生的CIDEP随时间倒转。这可以用三重态中自旋极化的反转来解释，这是由非平面结构转变为平面结构引起的。(4) 1-萘甲基氯光解离：通过1-萘甲基氯的直接光激发和三重态敏化反应获得1-萘甲基自由基的CIDEP光谱。从CIDEP图分析可知，1-萘基甲基氯从最低三态的低振动能级分解生成1-萘基甲基自由基和氯原子。

In this research project, we have carried out four projects using time resolved ESR technique. Results obtained are summarized as follows.(1) Energy Transfer to Higher Triplet State: It is quite difficult to know by the conventional optical spectroscopy what kind of triplet state of energy acceptor is produced in triplet-triplet energy transfer. However, we succeeded to me sure the energy transfer to higher triplet state(T_2) by the time-resolved ESR and to determine the T_2 energy.(2) Spin Polarization Transfer in the Triplet-Doublet Systems: Mechanism of spin polarization transfer was studied in the triplet-doublet systems Using relatively stable radicals as doublet sources. Since the spin polarization transfer occurred when the triplet energy was higher than the excitation energy of radicals, it is. concluded that the spin polarization transfer accompanies energy transfer.(3) Inversion of Spin Polarization in Benzil and alpha-Naphthil:CIDEP generated in the reactions benzil and alpha-naphthyl with aniline and phenol was inverted with time. This is explained by the inversion of spin polarization in the triplet state which is caused by the structural change from non-planar to planar one.(4) Photodissociation of 1-Naphthylmethylchloride: CIDEP spectra of 1-naphthylmethyl radicals was obtained by direct photoexcitation and triplet sensitized reactions of 1-naphthylmethylchloride. It is known from the analysis of CIDEP patterns that 1-naphthylmethylehloride decomposes from the low vibrational level of the lowest triplet state to yield 1-naphthylmethyl radicals and chlorine atoms.