UV absorption spectrum of the ClO dimer (Cl2O2) between 200 and 420 nm.
UV absorption spectrum of the ClO dimer (Cl2O2) between 200 and 420 nm.
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ClO 二聚体 (Cl2O2) 的紫外吸收光谱在 200 至 420 nm 之间。
DOI：
10.1021/jp9065345
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
J. B. Burkholder
中科院分区：
文献类型：
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作者：
D. Papanastasiou;V. Papadimitriou;D. Fahey;J. B. Burkholder
Cl（2）O（2）（过氧化二氯）的紫外光分解是催化破坏极地平流层臭氧的关键步骤。在这项研究中，气相紫外吸收光谱的Cl（2）O（2）的测量使用二极管阵列光谱和绝对截面，σ，报告的波长范围为200-420 nm。在低温（200-228 K）和高压（约700 Torr，He）条件下，用248 nm的脉冲激光光解Cl（2）O或351 nm的脉冲激光光解Cl（2）/Cl（2）O混合物，产生ClO自由基，然后通过ClO自反应生成Cl（2）O（2）。Cl（2）O（2）光谱是根据气相ClO自由基化学反应完成后记录的光谱获得的。光谱分析使用在271、312.9和408.5 nm处观察到的等吸收点，结合反应化学计量和氯质量平衡来确定Cl（2）O（2）光谱。Cl（2）O（2）UV吸收光谱峰值位于244.5 nm处，截面为7.6（-0.5）（+0.8）x 10（-18）cm（2）分子（-1），其中引用的误差限为2 σ，包括估计的系统误差。在300-420 nm波长范围内获得的Cl（2）O（2）吸收截面与Burkholder等人先前报道的Cl（2）O（2）光谱（J. Phys. Chem. A 1990，94，687）非常一致，并且显著高于Pope等人报道的值（J. Phys. Chem. A 2007，111，4322）。讨论了Cl（2）O（2）截面值与Pope等人研究结果不一致的可能解释。代表性的，大气光解速率系数计算和不确定性的范围估计的基础上确定的西格玛（Cl（2）O（2））（lambda）在这项工作中。尽管我们对Cl（2）O（2）光化学的基本理解仍有待提高，但这项工作表明，模拟观测到的极地臭氧消耗不需要对当前大气化学机制进行重大修订。
The UV photolysis of Cl(2)O(2) (dichlorine peroxide) is a key step in the catalytic destruction of polar stratospheric ozone. In this study, the gas-phase UV absorption spectrum of Cl(2)O(2) was measured using diode array spectroscopy and absolute cross sections, sigma, are reported for the wavelength range 200-420 nm. Pulsed laser photolysis of Cl(2)O at 248 nm or Cl(2)/Cl(2)O mixtures at 351 nm at low temperature (200-228 K) and high pressure (approximately 700 Torr, He) was used to produce ClO radicals and subsequently Cl(2)O(2) via the termolecular ClO self-reaction. The Cl(2)O(2) spectrum was obtained from spectra recorded following the completion of the gas-phase ClO radical chemistry. The spectral analysis used observed isosbestic points at 271, 312.9, and 408.5 nm combined with reaction stoichiometry and chlorine mass balance to determine the Cl(2)O(2) spectrum. The Cl(2)O(2) UV absorption spectrum peaks at 244.5 nm with a cross section of 7.6(-0.5)(+0.8) x 10(-18) cm(2) molecule(-1) where the quoted error limits are 2sigma and include estimated systematic errors. The Cl(2)O(2) absorption cross sections obtained for wavelengths in the range 300-420 nm are in good agreement with the Cl(2)O(2) spectrum reported previously by Burkholder et al. (J. Phys. Chem. A 1990, 94, 687) and significantly higher than the values reported by Pope et al. (J. Phys. Chem. A 2007, 111, 4322). A possible explanation for the discrepancy in the Cl(2)O(2) cross section values with the Pope et al. study is discussed. Representative, atmospheric photolysis rate coefficients are calculated and a range of uncertainty estimated based on the determination of sigma(Cl(2)O(2))(lambda) in this work. Although improvements in our fundamental understanding of the photochemistry of Cl(2)O(2) are still desired, this work indicates that major revisions in current atmospheric chemical mechanisms are not required to simulate observed polar ozone depletion.