Absorption cross-sections for the 5th and 6th vibrational overtones in a series of short chained alcohols using incoherent broadband cavity enhanced-absorption spectroscopy (IBBCEAS)
Absorption cross-sections for the 5th and 6th vibrational overtones in a series of short chained alcohols using incoherent broadband cavity enhanced-absorption spectroscopy (IBBCEAS)
复制标题
使用非相干宽带腔增强吸收光谱 (IBBCEAS) 绘制一系列短链醇中第五和第六振动泛音的吸收截面
DOI：
10.1016/j.jms.2023.111746
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发表时间：
2023
影响因子：
1.4
通讯作者：
Hansen, Jaron C.
中科院分区：
文献类型：
--
作者：
Flowerday, Callum E.;Bhardwaj, Nitish;Thalman, Ryan;Asplund, Matthew C.;Sevy, Eric T.;Hansen, Jaron C.
使用慢流电池和非相干宽带腔增强吸收光谱（IBBCEAS）测量气相甲醇、乙醇和异丙醇的第5（6←0）和第6(7←0)OH泛音的吸收截面。使用两种不同的仪器在447-457 nm和508-518 nm两个波长区域进行测量。实验结果与先前对这些跃迁的激发能的计算预测一致。将OH拉伸作为局部模式，可以计算所研究的每种醇的基本振动频率（ωe）、非调和常数（ωexe）和垂直解离能（VDE）。甲醇、乙醇和异丙醇的基本振动频率分别为3848±18 cm−1、3807±55 cm−1和3813±63 cm−1。甲醇、乙醇和异丙醇的非调和常数分别为84.8±2.1 cm−1、80.2±5.9 cm−1和84.4±6.8 cm−1。OH垂直解离能分别为499.4±18.4 kJ/mol、518.0±56.7 kJ/mol和492.7±59.9 kJ/mol。将光谱测量值与热力学测量的OH键离解能进行比较。与本文报道的值相比，先前的键离解能测量值所观察到的差异可以用垂直离解能和键离解能之间的差异来解释。如果OH泛音伸展模式在甲醇中被激发到第5或第6泛音，则甲醇与o2的双分子反应在热力学上是可行的，并且在适当的压力和温度组合下可以促进甲氧基和ho2自由基的形成。
Absorption cross-sections for the 5th (6 ← 0) and 6th (7 ← 0) OH overtones for gas-phase methanol, ethanol, and isopropanol were measured using a slow flow cell and Incoherent Broadband Cavity-Enhanced Absorption Spectroscopy (IBBCEAS). Measurements were performed in two wavelength regions, 447–457 nm, and 508–518 nm, using two different instruments. The experimental results are consistent with previous computational predictions of the excitation energies for these transitions. Treating the OH stretch as a local mode allowed for calculation of the fundamental vibrational frequency (ωe), anharmonicity constant (ωexe), and the vertical dissociation energy (VDE) for each alcohol studied. The fundamental vibrational frequency is 3848 ± 18 cm−1, 3807 ± 55 cm−1, and 3813 ± 63 cm−1for methanol, ethanol, and isopropanol, respectively. The anharmonicity constant was measured to be 84.8 ± 2.1 cm−1, 80.2 ± 5.9 cm−1, and 84.4 ± 6.8 cm−1for methanol, ethanol, and isopropanol, respectively. The OH vertical dissociation energy was measured to be 499.4 ± 18.4 kJ/mol, 518.0 ± 56.7 kJ/mol, and 492.7 ± 59.9 kJ/mol. The spectroscopically measured values are compared to thermodynamically measured OH bond dissociation energies. The observed differences in previous measurements of the bond dissociation energies compared to the values reported herein can be explained due to the difference between vertical dissociation energies and bond dissociation energies. If the OH overtone stretching mode is excited in methanol to either the 5th or 6th overtone, the bimolecular reaction between methanol and O2becomes thermodynamically feasible and could contribute to formation of methoxy and HO2radical under the proper combination of pressure and temperature.