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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Photodissociation Rate Constants for VUV Processes of CF_3Cl and CF_2Cl-2 in the Upper Atmosphere. A MQDO Study
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Photodissociation Rate Constants for VUV Processes of CF_3Cl and CF_2Cl-2 in the Upper Atmosphere. A MQDO Study

机译：大气上部CF_3Cl和CF_2Cl-2的VUV过程的光解离速率常数。 MQDO研究

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摘要

The availability of data concerning the upper atmosphere is essential for an understanding of both the change in solar activity and the different processes that have direct effects on the biosphere, in particular, those with harmful environmental consequences. The main goal of the present work is the theoretical analysis of the photodissociation of two chlorofluorocarbon (CFC) compounds that play an important role in the chemical and energetic balance of the upper atmosphere, CF_3Cl and CF_2Cl_2. Given that the molecular absorption cross section is directly linked to a molecule's photodissociation rate, we have first calculated cross sections and then have used the achieved values to determine the mechanisms of the photofragmentation processes that CF_3Cl and CF_2Cl_2 undergo at specific vacuum-UV (VUV) wavelengths that are present in the ionosphere. We have focused our study on the calculation of the kinetic rate constants for the processes that can give rise to cations upon photoabsorption, because they are difficult to determine experimentally. Through the analysis of the photodissociation rate constants, we have been able to make a comparative study of the dissociative behavior of CF3Cl and CF_2Cl_2 when these two CFC's undergo absorption within the VUV spectral region. The atmospheric photodissociation rate constants of CF_3Cl and CF_2Cl_2 have been calculated with the Molecular-adapted Quantum Defect Orbital (MQDO) approach as a function of the altitude and at different solar zenith angles. Altitudes from 60 to 150 km, which fall within the D and E layers of the ionosphere, have been considered. No earlier data of this kind have been found in the literature.
机译：关于高层大气的数据的可用性对于理解太阳活动的变化以及对生物圈有直接影响的不同过程，特别是对那些具有有害环境后果的过程的理解至关重要。本工作的主要目的是对两种在高层大气的化学和高能平衡中起重要作用的氯氟烃（CFC）化合物的光解的理论分析，CF_3Cl和CF_2Cl_2。考虑到分子吸收截面与分子的光解离速率直接相关，我们首先计算截面，然后使用获得的值确定CF_3Cl和CF_2Cl_2在特定真空-UV（VUV）下经历的光碎过程的机理。电离层中存在的波长。我们将研究的重点放在了可以通过光吸收引起阳离子的过程的动力学速率常数的计算上，因为它们很难通过实验确定。通过对光解离速率常数的分析，我们能够对CF3Cl和CF_2Cl_2在这两个CFC在VUV光谱范围内吸收时的解离行为进行比较研究。 CF_3Cl和CF_2Cl_2的大气光解离速率常数已通过分子适应量子缺陷轨道（MQDO）方法计算为海拔高度和在不同太阳天顶角下的函数。已经考虑了电离层D和E层内60至150 km的海拔。文献中未发现此类数据。

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