乙烯基和乙炔基离子的光谱和解离动力学

As two important intermediates of circumstellar chemistry and combustion process, vinyl and ethynyl radicals and their cation play the significant roles in developing the related chemical models, especially their ionization potentials and vibrational frequencies. However, their spectroscopic data are very scarce, and only a few IR spectra have been measured with inconsistent conclusions. Combined the home-made threshold photoelectron-photoion coincidence mass spectrometry with photoionization using VUV light from synchrotron radiation, photoionization of vinyl and ethynyl radicals and dissociation dynamics of their cations will be performed. Through applying the mass selected threshold photoelectron spectra, a new detection method of these radicals and their isomers will be developed. With the aid of some high-level quantum chemical calculations, the ionization energies of these radicals can be determined, as well as vibrational frequencies of the cations. Moreover, the released energy and angular distributions in dissociation of these radical ions in the excited states will be measured, and photodissociation mechanisms will be revealed. Therefore, more accurate spectroscopic data and dynamic information will be provided for the related chemical processes.

乙烯基、乙炔基及其离子是星际化学和燃烧化学中的重要中间物，其电离能和振动频率的测量对于相关模型的发展至关重要，然而迄今两种离子的光谱数据极为缺乏，仅有极少数红外光谱的报道，部分结果还不一致。为此，本项目中我们拟采用自行研制的阈值光电子—光离子符合质谱仪，以同步辐射真空紫外光源作为电离光，开展乙烯基C2H3和乙炔基C2H的光电离，以及它们的离子光解离动力学研究。利用质量选择的阈值光电子谱技术对热解产生的C2H3和C2H基实现有效测量，发展自由基及同分异构体的检测方法，并结合理论计算，不仅精确地确定生成不同离子同分异构体的绝热电离能、振动频率等基本数据，而且还将开展C2H3+和C2H+离子的激发态研究，测量其激发态解离碎片的能态分布和角度分布。在此基础上，我们期望在分子层次上深入理解这些自由基离子的光解离机理，为与之相关的星际化学和燃烧科学等领域的应用提供准确的光谱数据以及动力学参数。

我们以同步辐射真空紫外光源作为电离-解离光，利用自行研发的阈值光电子-光离子符合速度成像谱仪，完成了热解自由基源与符合谱仪的结合改造和测试，开展了大气环境和燃烧过程相关的若干碳氢分子体系（如C2H3Cl，CF3Cl，OCS，CH3F等）的电离-解离动力学研究和代表性体系（如碳酸二甲酯，硝基甲烷等）的高温热解动力学研究。其中，针对乙烯自由基（C2H3）的精确电离能测量，我们通过对比阈值光电子谱、光电离光谱的差异，结合高精度理论计算，解释了实验测量值差异的物理来源，给出了精确电离能的推荐值8.462 eV，与热力学数据库的最新结果8.477±0.007 eV基本一致；我们还开展了电子态选择的CF3Cl +离子解离动力学研究，通过测量各激发能量下的解离碎片符合速度影像获得了解离过程的平动能分布和角度分布信息，得到了离子出现势AP0(CF3+/CF3Cl) = 12.79±0.02 eV，对比了X2E, A2A'和B2A"电子态的C-Cl和C-F解离产物通道分支比和机理，验证了内转换过程是C2E和D2E电子态断键过程的速控步；结合量子化学计算和实验测量，阐明了C2H3Cl离子B2A"和C2A'电子态的耦合解离机理；同时，我们研发了新型电喷雾和激光溅射离子源与质谱的结合技术，申请了相关国家发明专利；此外，我们还开展了部分光化学和模型蛋白淀粉纤维化动力学的研究。执行期间，我们累计在国内外期刊Phys. Chem. Chem. Phys., J. Phys. Chem.等上发表SCI论文18篇，申请和授权国家发明专利3项。