Quantum-State-Selected Integral Cross Sections and Branching Ratios for the Ion–Molecule Reaction of N 2 + (X 2 Σ g + : ν + = 0–2) + C 2 H 4 in the Collision Energy Range of 0.05–10.00 eV
Quantum-State-Selected Integral Cross Sections and Branching Ratios for the Ion–Molecule Reaction of N 2 + (X 2 Σ g + : ν + = 0–2) + C 2 H 4 in the Collision Energy Range of 0.05–10.00 eV
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0.05～10.00 碰撞能量范围内 N 2 (X 2 Σ g : ν = 0–2) C 2 H 4 离子与分子反应的量子态选择积分截面和支化比
DOI：
10.1021/acs.jpca.8b04587
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发表时间：
2018
期刊：
影响因子：
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通讯作者：
Ng, Cheuk-Yiu
中科院分区：
文献类型：
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作者：
Xu, Yuntao;Xiong, Bo;Chang, Yih Chung;Ng, Cheuk-Yiu
利用真空紫外激光脉冲场电离光离子源和双四极-双八极离子导向滤质器，在质心动能Ecm = 0.05-10.00 eV范围内，获得了N2+（X2 ~（？）g+：ν+= 0-2）+C2 H4离子-分子反应的详细的量子振动态选择积分截面σν+，ν+= 0-2.三个主要产物通道对应于C2 H3+、C2 H2+和N2 H+离子的形成，其σν+值的顺序为σν+（C2 H3+）> σν+（C2 H2+）> σν+（N2 H+）。小的σν ~+（N_2H ~+）通道被Ecm强烈抑制，仅在Ecm <0.70eV时观察到。高的σν+（C2 H3+）和σν+（C2 H2+）值表明C2 H3+和C2 H2+产物离子是通过近能量共振电荷转移机制产生的内激发C2 H4+（C2 H4 +*）中间体的迅速解离形成的。发现在0.05-6.00 eV范围内，σν+（C_2H_3 ~+）和σν+（C_2H_2 ~+）仅轻微下降或几乎保持恒定。这一观察结果与通常对于放热反应途径观察到的σν+值随着Ecmis增加而急剧下降的预期相反。当σν ~+（C_2H_3 ~+）和σν ~+（C_2H_2 ~+）在ν ~+= 2和Ecm = 0.20-7.00 eV范围内，观察到明显的振动增强.通过在固定的Ecm值下同时测量产物C_2H_3 ~+、C_2H_2 ~+和N_2H ~+离子的强度，也可以高精度地确定分支比σν ~+（C_2H_3 ~+）：σ ν ~+（C_2H_2 ~+）：σν ~+（N_2H ~+）。这里报告的σν+和分支比值对行星大气的化学成分和演变的现实建模所需的数据库是有用的贡献，例如提香的电离层。量子态选择性的结果也可以作为基础化学反应动力学理论计算的实验基准。
By implementing a vacuum ultraviolet laser-pulsed field ionization-photoion ion source with a double quadrupole–double octopole ion guide mass filter, we have obtained detailed quantum-vibrational-state-selected integral cross sections σν+, ν+= 0–2, for the ion–molecule reaction of N2+(X2Σg+: ν+= 0–2) + C2H4in the center-of-mass kinetic energy range ofEcm= 0.05–10.00 eV. Three primary product channels corresponding to the formation of C2H3+, C2H2+, and N2H+ions are identified with their σν+values in the order of σν+(C2H3+) > σν+(C2H2+) > σν+(N2H+). The minor σν+(N2H+) channel is strongly inhibited byEcmand observed only atEcm< 0.70 eV. The high σν+(C2H3+) and σν+(C2H2+) values indicate that C2H3+and C2H2+product ions are formed by prompt dissociation of internally excited C2H4+(C2H4+*) intermediates produced via the near-energy-resonance charge-transfer mechanism. The σν+(C2H3+) and σν+(C2H2+) are found to drop only mildly or stay nearly constant as a function ofEcmin the range of 0.05–6.00 eV. This observation is contrary to the expectation of a steep decline for the σν+value commonly observed for an exothermic reaction pathway asEcmis increased. Significant vibrational enhancement is observed for the σν+(C2H3+) and σν+(C2H2+) at ν+= 2 and in theEcmrange of ∼0.20–7.00 eV. The branching ratios σν+(C2H3+):σν+(C2H2+):σν+(N2H+) are also determined with high precision by measuring the intensities of product C2H3+, C2H2+, and N2H+ions simultaneously at fixedEcmvalues. The σν+and branching ratio values reported here are useful contributions to the database needed for realistic modeling of the chemical compositions and evolutions of planetary atmospheres, such as the ionosphere of Titian. The quantum-state-selective results can also serve as experimental benchmarks for theoretical calculations on fundamental chemical reaction dynamics.