【作者】 朱光来；

【导师】 崔执凤；

【作者基本信息】 安徽师范大学 ， 原子与分子物理， 2004， 硕士

【摘要】 化学诱导动态电子自旋极化（CIDEP）是由于顺磁粒子在其自旋能级间的非Boltzmann分布导致的。对于光解瞬态自由基的CIDEP，可以用时间分辨电子自旋共振（TRESR）波谱技术对其检测。CIDEP为光物理和光化学过程提供了大量的信息，是研究反应中间体、电子转移和能量转移等的有效手段之一。 本论文在简要论述自旋极化基本理论的基础上，定量地分析了不同延时下激光光解对苯醌的CIDEP谱中各机理对极化贡献的比例；从实验上研究了对苯醌和丙酮在不同体系中的CIDEP以及PH值和胶束环境对极化的影响；考虑零场分裂参数E，从理论上全面计算了自由基-三重态对极化机理的电子自旋极化强度。 第一章为绪论部分，简要概述了电子自旋共振（ESR）的基本原理以及CIDEP的基本概念，评述了光解自由基的CIDEP的发展现状。 第二章在介绍产生CIDEP的四种机理和TRESR波谱仪的原理和结构的基础上，实验研究了对苯醌／乙二醇（PBQ／EG）体系在不同激光延时下的TRESR谱，并对实验谱进行了计算机模拟。通过对不同机理在不同延时下对各自由基极化强度贡献的对比，说明由TM形成的PBQH的极化比由RPM形成的PBQH^·的极化衰减快，这是由于不同机理产生的自由基的极化衰减速率不同造成的。 第三章为实验部分，研究了对苯醌和丙酮（ACETONE）在不同体系中的CIDEP，以及胶束环境的影响。 激光光解对苯醌，在1，2-丙二醇（PG）均相溶液中得到了以TM为主的苯半醌自由基PBQH^·，加入硫酸后，我们观察到了质子交换现象；在甲酰胺中，则只得到了苯醌负离子基PBQ^·-，硫酸的加入，使得PBQ^·-的五条峰逐步转变为PBQH^·的六条双峰，证明PBQ^·-是由PBQH^*解离产生的。 对ACETONE/EG（PG）体系，光解得到了丙酮拨自由基（c H3）2 C OH不!J乙二醇碳自山基CHZOllel:o一I以及l，2一丙二醇碳自由基CH。COHCHOH的发射/吸收（E/A）型极化信号，这是一个即M极化过程。在酸性环境中，溶剂分子的极化信号明显减弱，而对（cH。）2 COH自由基的极化没有什么影响;在碱性环境中，则反应生成了负离子基（c H3）ZCO一。 在胶束环境中，不同表面活性剂以及不同的浓度对体系极化的影响是不{司的。}泪离子表面活性剂CTAB对体系中生成的自山基的极化机理没有产生影响，而加入体系中TX一100的浓度对体系的极化机理却产生了很大的形响。在PBQ/PG体系中，TX一100的加入，使得该体系光解后生成了PBQ’一;而在ACETONE/ PG体系「}一，，随着TX一100浓度的增加，TM机理刘极化强度的贡献明显增大。同时就胶束环境对CIDEP的影响作了初步的词一沦和分析。 第四章为理论计算部分。在前面工作的丛础上，以光敏剂分子激发三重态和稳态自山基形成缔合体为模型，利用角动量理论、二阶微扰理论和密度矩阵理沦，在考虑零场分裂参数E的作用的基础上，对DP一RTPM以及QP一RTPM极化强度，进行了史进一步的理论计算。结果表明，零场分裂多数E，使净极化E（A）减弱，}司时使超精细相关极化E/A（刀E）加强。更多还原

【Abstract】 The phenomenon of transient populations in electron spin states deviating from the Boltzmann distribution has been known as chemically induced dynamic electron polarization (CIDEP), which can be tested by time-resolved ESR (TRESR). CIDEP can give us more information about photochemical and photophysical processes and it is a useful method to study intermediate species, electron transfer and energy transfer mechanisms in reactions.In this paper, based on the brief summary of the fundamental theory of electron spin polarization, the contributions from triplet mechanism(TM) and radical pair mechanism (RPM) to the CIDEP of p-benzoquinone/ethylene glycol (PBQ/EG) system was quantitatively analyzed. The CIDEP of laser photolysis of PBQ and acetone in different homogenous solutions and micelles solutions were experimentally studied. At the same time, considering the zero-field-splitting constant E, the electron spin polarization due to radical-triplet pair mechanism (RTPM) is theoretically calculated in detail.In chapter one, the fundamental principles of ESR and the definition of CIDEP as well as its current development were described respectively.In chapter two, the four mechanisms to generate CIDEP were introduced and the experiment instrument was described briefly. The CIDEP spectrum of PBQ/EG system has been obtained experimentally by using 285nm laser photolysis. Compared with the stimulated spectra, the relative CIDEP intensity from TM and RPM at different time delay was quantitatively analyzed. It was concluded that the polarization of p-benzosemiquinone radical PBQH* produced from TM decayed faster than generated from RPM.In chapter three, the CIDEP of the photolyzed radicals of PBQ and acetone in different homogenous solutions were experimentally studied and the influence of micellar microenvironment on the generation of CIDEP were discussed.The major peaks of PBQH’ generated from TM was obtained inPBQ/propylene glycol (PG) system and the proton exchange phenomenon was observed with the addition of H2SO4. In PBQ/formamide (FM) system, only the five hyperfine peaks of PBQ- were obtained and the six double peaks of PBQH appeared with the addition of H2SO4 which indicated PBQ- was formed from the dissociation of PBQH*.When the acetone/EG (PG) system was photolyzed, the E/A pattern CIDEP spectrum of (CH3)2COH and CH2OHCHOH( CH3 COHCHOH ) generated fromRPM were obtained. In acid environment, the signal of CH2OHCHOH(CH3 COHCHOH) decreased evidently. In basic environment, (CH3)2CO- wasproduced.In micellar microenvironment, different surfactant and different concentration have different influence on CIDEP. With the addition of CTAB to sample solution, the polarization mechanism and the signal intensity were the same as in homogenous solutions. When PBQ/PG/TX-100 micellar solution was irradiated by the laser, the CIDEP signal of PBQ- was obtained except for the signal of PBQH’. When ACETONE/EG (PG) /TX-100 micellar solution was photolyzed, the TM appeared accompanying the RPM and the relative ratio oi’TM to RPM increased with the increasing of TX-100 concentration. Here, the fluence of micellar invironment on the generation of CIDEP was simply discussed and analyzed.In chapter four, based on the angular momentum theory, the second-order pcrLurbation theory and the motion equation of density matrix, the polarization intensity on the stable radicals of the QP-RTPM and DP-RTPM, with the zero-spilling-field constant E involved in the Hamiltonian, were calculated in detail, respectively. The results indicated that the polarization pattern is E+E/A or A+A/E. Furthermore, the results indicated that the zero-spilling-field constant E made the net polarization decrease and the hyperfine-dependent polarization increase.更多还原