NO2 电子吸收光谱的温度依赖性,The Journal of Physical Chemistry A

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NO2 电子吸收光谱的温度依赖性
The Journal of Physical Chemistry A ( IF 2.7 ) Pub Date : 2023-06-29 , DOI: 10.1021/acs.jpca.3c02832
Steve Ndengué ₁ , Ernesto Quintas-Sánchez ₂ , Richard Dawes ₂ , Christopher C Blackstone ₃ , David L Osborn _{3,

4}

Affiliation

二氧化氮 (NO ₂ ) 自由基由大气中最丰富的两种元素组成，可以通过多种方式形成，包括燃烧、高能材料爆炸和闪电。也与烟雾和臭氧循环相关，这些过程一起跨越了很宽的温度范围。值得注意的是，高分辨率 NO ₂电子吸收光谱仅在低于约 300 K 的狭窄范围内被报道。之前，我们报道过 [ J. Phys. 化学。A 2021 , 125 , 5519−5533] NO ₂最低四个电子态（X̃、à、B̃ 和 C̃）的准绝热势能面（PES）的构造。除了基于明确相关的 MRCI(Q)-F12/VTZ-F12从头开始数据的三维 PES 之外，偶极子和过渡偶极子的每个组件的几何依赖性也被映射到拟合表面。然后使用多构型时间相关 Hartree (MCTDH) 方法利用这些能量和跃迁偶极子表面计算 0 K 电子吸收光谱（来自地面振动初始状态）。在这里，作为这项工作的延伸，我们报告了一项关于高温对光谱影响的研究，考虑了旋转和振动激发初始态总体的影响。新的实验测量对计算进行了补充。计算了N = 20以内的数百个旋转状态和 200 个单独表征的振动状态的光谱贡献。我们开发了一种光谱模拟工具，可以对不同温度下的光谱进行建模——通过配分函数对各个光谱贡献进行加权，或者针对纯激发初始态（可以通过瞬态吸收光谱进行探测）。我们根据高温下的实验吸收光谱数据以及通过 (1,0,1) 初始振动状态的新测量来验证这些结果。

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Temperature Dependence of the Electronic Absorption Spectrum of NO2

The nitrogen dioxide (NO₂) radical is composed of the two most abundant elements in the atmosphere, where it can be formed in a variety of ways including combustion, detonation of energetic materials, and lightning. Relevant also to smog and ozone cycles, together these processes span a wide range of temperatures. Remarkably, high-resolution NO₂ electronic absorption spectra have only been reported in a narrow range below about 300 K. Previously, we reported [ J. Phys. Chem. A 2021, 125, 5519−5533] the construction of quasi-diabatic potential energy surfaces (PESs) for the lowest four electronic states (X̃, Ã, B̃, and C̃) of NO₂. In addition to three-dimensional PESs based on explicitly correlated MRCI(Q)-F12/VTZ-F12 ab initio data, the geometry dependence of each component of the dipoles and transition dipoles was also mapped into fitted surfaces. The multiconfigurational time-dependent Hartree (MCTDH) method was then used to compute the 0 K electronic absorption spectrum (from the ground rovibrational initial state) employing those energy and transition dipole surfaces. Here, in an extension of that work, we report an investigation into the effects of elevated temperature on the spectrum, considering the effects of the population of rotationally and vibrationally excited initial states. The calculations are complemented by new experimental measurements. Spectral contributions from hundreds of rotational states up to N = 20 and from 200 individually-characterized vibrational states were computed. A spectral simulation tool was developed that enables modeling the spectrum at various temperatures─by weighting individual spectral contributions via the partition function, or for pure excited initial states, which can be probed via transient absorption spectroscopy. We validate these results against experimental absorption spectroscopy data at high temperatures, as well as via a new measurement from the (1,0,1) initial vibrational state.

更新日期：2023-06-29

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