有机硫化物是大气主要污染物之一,其在大气中的光解产物还将造成二次污染,除了存在于有机硫化物中, S―S键还存在于胱氨酸等蛋白质中, S―S键的形成和断裂决定该类蛋白质的活性.本工作中,我们研究了用实验室常见的Nd:YAG激光器的四倍频266 nm激光光解C2H5SSC2H5过程,通过激光诱导荧光(LIF)光谱方法检测乙硫自由基C2H5S等光解产物.实验表明266 nm激光主要光解C2H5SSC2H5的S―S键产生C2H5S自由基.本文应用密度泛函理论的Becke3-Lee-Yang-Parr泛函(B3LYP方法)得到C2H5SSC2H5的S―S键、C―S键和C―C键的解离势能曲线,可知在266 nm光解条件下, C2H5SSC2H5在基态能够发生S―S键、C―S键解离, C―C键不发生解离.本文采用全活化空间自洽场(CASSCF)方法优化得到态和态的C2H5S自由基结构及其跃迁的绝热激发能,以辅助解析实验检测的C2H5S自由基的LIF光谱.实验结合理论计算最终得出,本实验266 nm光解条件下, C2H5SSC2H5主要发生S―S键解离,不排除少量分子发生C―S键解离的可能性. Organic sulfides are an atmospheric pollutant that photolyze in the atmosphere, causing additional pollution. The S―S bond exists not only in organic sulfides but also in some proteins such as L-cystine, and this bond is crucial to the bioactivity of this protein. In this work, we studied C2H5SSC2H5 photolysis at 266 nm, which is the quadruplicated frequency of the common Nd:YAG laser. The laser-induced fluorescence (LIF) spectra detected the photolyzed products, C2H5S radical. Our results show that the C2H5S radical was mainly created by dissociation of the S―S bond in C2H5SSC2H5. We determined the potential energy curves of the S―S, C―S, and C―C bonds in C2H5SSC2H5 at the B3LYP/6-311++G(d, p) level, finding that photolysis at 266 nm caused the S―S and C―S bonds of C2H5SSC2H5 to dissociate at the ground???2029-1??? state. Nevertheless, photolysis at 266 nm did not photolyze the C―C bond of C2H5SSC2H5. By optimizing the Cs geometry of the C2H5S radical at the???2029-1??? state and the???2029-2??? state, we determined the???2029-2???-???2029-1??? adiabatic transition energy at the CASSCF/6-311++G(d, p) level, and then studied the LIF spectra of the C2H5S radical. The main pathway is dissociation of the S―S bond of C2H5SSC2H5, though the C―S bond in a few C2H5SSC2H5 molecules did dissociate
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