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Quantum chemical intensity determinations of overlapped gas phase infrared bands.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy ( IF 4.3 ) Pub Date : 2020-01-13 , DOI: 10.1016/j.saa.2020.118067
Leonardo J Duarte 1 , Wagner E Richter 2 , Arnaldo F Silva 3 , Roy E Bruns 1
Affiliation  

The largest source of experimental error in determining gas phase fundamental infrared intensities arises from the separation of overlapped bands. Quantum chemical calculations at the QCISD/cc-pVTZ and QCISD/aug-cc-pVTZ levels were carried out on four simple hydrocarbons and the fluoro- and chloromethanes with the aim of accurate overlapped band separation. Fundamental vibrational intensity results were compared with individual empirical intensity estimates reported for overlapped band systems. Root mean square differences of 3.7 km mol-1 are found between the experimental and QCISD/cc-pVTZ values for nine overlapped bands of the hydrocarbons and 11.8 km mol-1 for the QCISD/aug-cc-pVTZ values for 12 overlapped bands of the fluoro- and chloromethanes. These values correspond to 14% and 18% of the average hydrocarbon and halomethane intensity values. Previous experimental separation errors were estimated to be quite larger, between 20% and 50%. As quantum calculations are continuously being refined one can expect more accurate band separation results in the future.

中文翻译:

气相气相重叠红外光谱的量子化学强度测定。

确定气相基本红外强度的最大实验误差来源是重叠谱带的分离。QCISD / cc-pVTZ和QCISD / aug-cc-pVTZ含量的量子化学计算是对四种简单的烃以及氟代和氯代甲烷进行的,目的是进行精确的重叠谱带分离。将基本振动强度结果与重叠带系统报告的单个经验强度估计值进行比较。在9个碳氢化合物重叠谱带的实验值和QCISD / cc-pVTZ值之间发现了3.7 km mol-1的均方根差,对于12个碳氢化合物重叠谱带的QCISD / aug-cc-pVTZ值发现了11.8 km mol-1。氟甲烷和氯甲烷。这些值分别相当于平均碳氢化合物和卤甲烷强度值的14%和18%。以前的实验分离误差估计很大,在20%至50%之间。随着量子计算的不断完善,人们有望在未来获得更准确的能带分离结果。
更新日期:2020-01-13
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