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在室温(298±2)K、大气压(1×105Pa)下,分别测定了HO2及HO2+OH混合自由基在化学放大过程中的水效应,发现水效应不随自由基的类型有显著变化.在此基础上,采用密度泛函理论在CCSD(T)/6-311G(2d,2p)//B3LYP/6-311G(2d,2P)水平上研究了HO2自由基-水加合物HO2·H2O与NO的反应.计算结果表明HO2·H2O与NO主反应通道为HO2·H2O+NO→HNO3+H2O(R4a).应用Polyrate程序计算了(R4a)的速率常数.在200~2000K温度范围内,拟合得到该反应速率常数的三参数Arrenhnius方程为:k=5.49×107T1.03exp(-14798/T).将理论计算结果用于模式计算中模拟得到的水效应曲线与实验测定曲线一致,表明(R4a)可能是形成水效应的主要原因.
At room temperature (298 ± 2) K, atmospheric pressure (1 × 105Pa), the water effect of HO2 and HO2 + OH mixed radicals in chemical amplification process was measured and found that the water effect does not significantly change with the type of free radical. On this basis, the effects of HO2 radical-water adduct HO2 · H2O on the CCSD (T) / 6-311G (2d, 2p) // B3LYP / 6-311G (2d, 2P) With NO. The calculated results show that the main reaction channel between HO2 · H2O and NO is HO2 · H2O + NO → HNO3 + H2O (R4a) .The rate constant of (R4a) was calculated by Polyrate program.Under the temperature range of 200 ~ 2000K, The three-parameter Arrenhnius equation fitting to the reaction rate constant is: k = 5.49 × 107T1.03exp (-14798 / T). The theoretical calculation results are consistent with the experimental measurement curve in the model calculation, which shows that (R4a) may be the main reason for the water effect.