物理化学学报 >> 2005, Vol. 21 >> Issue (05): 539-543.doi: 10.3866/PKU.WHXB20050516

研究论文 上一篇    下一篇

五氟乙烷的真空紫外光电离光解离

杨斌; 黄超群; 杨锐; 卫立夏; 王晶; 王思胜; 单晓斌; 齐飞; 张允武; 盛六四; 王振亚; 郝立庆; 周士康   

  1. 中国科学技术大学国家同步辐射实验室,合肥   230029;   中国科学院安徽光学精密机械研究所环境光谱学实验室,合肥   230031
  • 收稿日期:2004-11-19 修回日期:2005-01-25 发布日期:2005-05-15
  • 通讯作者: 盛六四 E-mail:lssheng@ustc.edu.cn

Vacuum Ultraviolet Photoionization and Photodissociation of Pentafluoroethane

YANG Bin; HUANG Chao-Qun; YANG Rui; WEI Li-Xia; WANG Jing; WANG Si-Sheng; SHAN Xiao-Bin; QI Fei; ZHANG Yun-Wu; SHENG Liu-Si; WANG Zhen-Ya; HAO Li-Qing; ZHOU Shi-Kang   

  1. National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei   230029;  Laboratory of Environmental Spectroscopy, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei   230031
  • Received:2004-11-19 Revised:2005-01-25 Published:2005-05-15
  • Contact: SHENG Liu-Si E-mail:lssheng@ustc.edu.cn

摘要: 利用同步辐射真空紫外光电离结合飞行时间质谱对五氟乙烷(CHF2CF3)进行了光电离光解离的研究,测定了CHF2CF3的电离势及该分子主要碎片离子的出现势. 结果表明: CHF2CF3的绝热电离势为(12.25±0.10) eV, 主要碎片离子有CF2CF3+、CHFCF3+、CF2CF2+、CF3+、CHF2+、CHF+和CF+,其出现势分别为 (13.93±0.10) eV, (15.25±0.10) eV, (15.12±0.10) eV, (13.30±0.05) eV, (13.05±0.08) eV, (19.17±0.10) eV和 (19.56±0.15) eV. 另外,用从头算分子轨道理论计算了解离电离过程中所有碎片的总能量,并给出了电子态及对称性. 根据实验结果和理论计算,分析了可能的解离通道,并得到了分子及母体离子的键解离能等重要的热力学数据.

关键词: 五氟乙烷, 光电离, 出现势, 解离能

Abstract: The vacuum ultraviolet photoionization and photodissociation of pentafluoroethane have been studied by using synchrotron radiation. The ionization potential of pentafluoroethane is determined to be (12.25±0.10) eV. Photoionization efficiency (PIE) curves for CF2CF3+、CHFCF3+、CF2CF2+、CF3+、CHF2+、CHF+ and CF+ have been measured. The appearance potentials (AP) of these ions are obtained from their PIE curves, and they are (13.93±0.10) eV, (15.25±0.10) eV, (15.12±0.10) eV, (13.30±0.05) eV, (13.05±0.08) eV, (19.17±0.10) eV and (19.56±0.15) eV, respectively. In addition, the energetics of the dissociative photoionizations have been examined by ab initio Gaussian-3 calculations. The computational results are useful in establishing the dissociation channels near the ionization thresholds. According to the experimental results and the energies calculated by Gaussian-3 theory, the main possible pathways of the photodissociation have been analyzed. And the dissociation energies of the molecule and its cation have been derived from experiment and calculation.

Key words: Pentafluoroethane, Photoionization, Appearance potential, Dissociation energy