Potential Nonstatistical Effects on the Unimolecular Decomposition of H2O2
Potential Nonstatistical Effects on the Unimolecular Decomposition of H2O2
复制标题
对 H2O2 单分子分解的潜在非统计影响
DOI：
10.1021/acs.jpca.2c03501
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发表时间：
2022
期刊：
影响因子：
2.9
通讯作者：
Akira Matsugi
中科院分区：
文献类型：
--
作者：
犬飼啓登，多田幸生，春木将司;義岡秀晃;Akira Matsugi
试图评估过氧化氢（H2 O2）热分解的非统计效应。以前对该反应的实验研究报道了速率常数的不寻常的压力依赖性，表明比传统理论预期的更广泛的衰减行为。本文基于H2 O2和H2 O2 + Ar的全局势能面上的经典轨道计算，研究了非统计效应对反应速率常数的影响.重点是分子内的能量重新分配从theK-转子，即外部转子的旋转主轴的最小转动惯量。对H_2O_2分子在解离阈值以上激发态的计算表明，从扭转和K-转子到振动的能量重新分配与解离是竞争性的。特别是，与theK-转子相关的能量的缓慢重新分配显着影响解离速率。H_2O_2与Ar碰撞的连续轨迹计算表明，与K-转子相关的能量可以比振动能量更有效地碰撞转移。基于这些结果和几个假设，提出了一个简单的模型来解释压力依赖的热速率常数的非统计效应。该模型预测显着扩大的衰减曲线的速率常数，但仍然不能完全解释实验数据。
An attempt is made to evaluate the nonstatistical effects in the thermal decomposition of hydrogen peroxide (H2O2). Previous experimental studies on this reaction reported an unusual pressure dependence of the rate constant indicating broader falloff behavior than expected from conventional theory. In this work, the possibility that the rate constant is affected by nonstatistical effects is investigated based on classical trajectory calculations on the global potential energy surfaces of H2O2and H2O2+ Ar. The emphasis is on the intramolecular energy redistribution from theK-rotor, that is, the external rotor for rotation around the principal axis of least moment of inertia. The calculations for the H2O2molecules excited above the dissociation threshold suggest that the energy redistribution from the torsion andK-rotor to vibrations can be competitive with dissociation. In particular, the slow redistribution of the energy associated with theK-rotor significantly affects the dissociation rate. The successive trajectory calculations for collisions of H2O2with Ar show that the energy associated with theK-rotor can be collisionally transferred more efficiently than the vibrational energy. On the basis of these results and several assumptions, a simple model is proposed to account for the nonstatistical effects on the pressure-dependent thermal rate constants. The model predicts significant broadening of the falloff curve of the rate constants but still cannot fully explain the experimental data.