Optical frequency comb-based measurements and the revisited assignment of high-resolution spectra of CH 2 Br 2 in the 2960 to 3120 cm -1 region
Optical frequency comb-based measurements and the revisited assignment of high-resolution spectra of CH 2 Br 2 in the 2960 to 3120 cm -1 region
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基于光学频率梳的测量和CH 2 Br 2 2960至3120 cm -1 区域高分辨率光谱的重新分配
DOI：
10.1039/d2cp05881b
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发表时间：
2023
影响因子：
3.3
通讯作者：
Sadiek I
中科院分区：
文献类型：
--
作者：
Sadiek I
溴化有机化合物是源自海洋的有毒微量气体，会影响大气的氧化能力并造成其溴负担。由于缺乏准确的吸收截面数据以及严格的光谱模型，这些气体的定量光谱检测受到限制。本研究通过两种基于光学频率梳的方法，傅里叶变换光谱和基于虚拟成像相控阵的空间色散方法，测量了2960 cm - 1至3120 cm - 1范围内二溴甲烷CH2Br2的高分辨率光谱。用两种光谱仪测量的综合吸收截面在4%以内具有很好的一致性。介绍了对测量光谱的重新考察的旋转振动分配，其中特征的进展归因于热带，而不是像以前那样归因于不同的同位素。总的来说，CH281Br2、CH279Br81Br和CH279Br2三个同位素体分别有12个振动跃迁。这四个振动跃迁归因于基本ν6带和附近的nν4 + ν6−nν4热带（n = 1-3），这是由于在室温下Br-C-Br弯曲振动的低处ν4模式的填充。新的模拟结果表明，由玻尔兹曼分布因子预测的强度与实验结果非常吻合。基谱和热带谱显示出强QKa(J)转振子团簇的递进。这些子簇的带头被分配并拟合到测量光谱中，提供了精确的带原点和12个状态的旋转常数，平均误差为0.0084 cm−1。以CH279Br81Br同位素体ν6波段的起始点、旋转常数和离心常数为拟合参数，对CH279Br81Br的ν6波段进行了详细拟合，平均误差为0.0011 cm−1。
Brominated organic compounds are toxic ocean-derived trace gases that affect the oxidation capacity of the atmosphere and contribute to its bromine burden. Quantitative spectroscopic detection of these gases is limited by the lack of accurate absorption cross-section data as well as rigorous spectroscopic models. This work presents measurements of high-resolution spectra of dibromomethane, CH2Br2, from 2960 cm−1 to 3120 cm−1 by two optical frequency comb-based methods, Fourier transform spectroscopy and a spatially dispersive method based on a virtually imaged phased array. The integrated absorption cross-sections measured using the two spectrometers are in excellent agreement with each other within 4%. A revisited rovibrational assignment of the measured spectra is introduced, in which the progressions of features are attributed to hot bands rather than different isotopologues as was previously done. Overall, twelve vibrational transitions, four for each of the three isotopologues CH281Br2, CH279Br81Br, and CH279Br2, are assigned. These four vibrational transitions are attributed to the fundamental ν6 band and the nearby nν4 + ν6 − nν4 hot bands (with n = 1–3) due to the population of the low-lying ν4 mode of the Br–C–Br bending vibration at room temperature. The new simulations show very good agreement in intensities with the experiment as predicted by the Boltzmann distribution factor. The spectra of the fundamental and the hot bands show progressions of strong QKa(J) rovibrational sub-clusters. The band heads of these sub-clusters are assigned and fitted to the measured spectra, providing accurate band origins and the rotational constants for the twelve states with an average error of 0.0084 cm−1. A detailed fit of the ν6 band of the CH279Br81Br isotopologue is commenced after assigning 1808 partially resolved rovibrational lines, with the band origin, rotational, and centrifugal constants as fit parameters, resulting in an average error of 0.0011 cm−1.