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The vacuum ultraviolet laser photochemistry of CO2 molecule and threshold photoelectron studies of hydrocarbon radicals by velocity-map imaging method.

机译：利用速度图成像方法研究了CO2分子的真空紫外激光光化学和碳氢化合物自由基的阈值光电子研究。

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摘要

By employing two independently tunable vacuum ultraviolet (VUV) laser radiations in tandem with the velocity-map imaging photoion (VMI-PI) apparatus, state-to-state photodissociation of CO2 has been investigated in the VUV energy range between 101.5 and 107.2 nm.;The spin-allowed CO + O product channels, CO(X 1Sigma+) + O(1D), CO(X 1Sigma+) + O(1S), and CO( a 3&Pgr;) + O(3P) and the spin-forbidden dissociation channel, CO(X1Sigma +) + O(3P), were directly observed VMI-PI images. By detecting photofragment atoms of O(3P2,1,0), O( 1D), and O(1S) via VMI-PI detection scheme, we have determined the vibrational-state distributions of the CO fragments. The total kinetic energy release spectra of the CO(X 1Sigma +) + O(1D) and CO(X 1Sigma +) + O(1S) reveal substantial differences in the CO vibrational-state distribution produced from different CO2 predissociative states. By using the VUV-Visible photoionization scheme of O(3P2,1,0) atoms, we have measured the spin-orbit branching ratios between the spin-allowed CO(a 3&Pgr;) + O(3P2,1,0) and spin-forbidden CO(X 1Sigma+) + O(3P2,1,0) channels from O(3P2,1,0) ion images. We have directly detected all the thermodynamically available CO + O dissociation channels (eq. 1-3, and 5) between 101.5 and 107.2 nm in CO2 photodissociation. Besides the CO + O products for the photodissociation of CO2 molecule, we provided the first experimental evidence for the formation of C( 3P) + O2(X 3Sigma g-) product mixtures between 101.5 and 107.2 nm in CO2 photodissociation. Our results indicate that all the energetically accessible channels (eq. 1-5) should be included in the CO2 photochemcial reaction networks. We have also combined the VUV laser with VMI method to measure the photoionization energies and vibrational energies of the cationic transient radical species, including C3H3, C3H5, CH 2Cl, and CH2Br. This newly developed technique has been proved to achieve higher detection efficiency and comparable resolution compared to the traditional pulsed-field ionization photoelectron (PFI-PE) method, making it an ideal alternative to record high-resolution photoelectron spectra of transient radical species with superior resolution and signal to noise ratio.
机译：通过与速度图成像光电离（VMI-PI）装置一起使用两个独立可调谐的真空紫外（VUV）激光辐射，已经研究了在101.5和107.2 nm之间的VUV能量范围内CO2的状态间光解离。 ;自旋允许的CO + O乘积通道，CO（X 1Sigma +）+ O（1D），CO（X 1Sigma +）+ O（1S）和CO（a 3＆Pgr;）+ O（3P）和自旋禁止解离通道，CO（X1Sigma +）+ O（3P），直接观察到VMI-PI图像。通过VMI-PI检测方案检测O（3P2,1,0），O（1D）和O（1S）的光碎原子，我们确定了CO碎片的振动状态分布。 CO（X 1Sigma +）+ O（1D）和CO（X 1Sigma +）+ O（1S）的总动能释放谱显示，CO振动态分布由不同的CO2预离解态产生很大差异。通过使用VUV可见的O（3P2,1,0）原子光电离方案，我们测量了自旋允许的CO（a 3＆Pgr;）+ O（3P2,1,0）与自旋之间的自旋轨道分支比-O（3P2,1,0）离子图像禁止使用CO（X 1Sigma +）+ O（3P2,1,0）通道。我们已经直接检测到在CO2光解离中101.5和107.2 nm之间的所有热力学可用的CO + O解离通道（方程1-3和5）。除了用于CO2分子光解的CO + O产物外，我们提供了在CO2光解中101.5至107.2 nm之间形成C（3P）+ O2（X 3Sigma g-）产物混合物的第一个实验证据。我们的结果表明，所有能量可利用的通道（等式1-5）都应包括在CO2光化学反应网络中。我们还将VUV激光与VMI方法相结合，以测量阳离子瞬态自由基物种（包括C3H3，C3H5，CH 2Cl和CH2Br）的光电离能和振动能。与传统的脉冲场电离光电子（PFI-PE）方法相比，这种新开发的技术已被证明具有更高的检测效率和相当的分辨率，使其成为记录具有更高分辨率的瞬态自由基物种的高分辨率光电子光谱的理想选择和信噪比。

著录项

  • 作者

    Lu, Zhou.;

  • 作者单位

    University of California, Davis.;

  • 授予单位 University of California, Davis.;
  • 学科 Physical chemistry.
  • 学位 Ph.D.
  • 年度 2015
  • 页码 165 p.
  • 总页数 165
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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