Direct Observation and Quantitative Measurement of OH Radical Desorption During the Ultraviolet Photolysis of Liquid Nonanoic Acid
Direct Observation and Quantitative Measurement of OH Radical Desorption During the Ultraviolet Photolysis of Liquid Nonanoic Acid
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液体壬酸紫外光解过程中OH自由基脱附的直接观察和定量测量
DOI：
10.1021/acs.jpclett.2c02199
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
and Tetsuya Hama
中科院分区：
文献类型：
--
作者：
Naoki Numadate;Shota Saito;Yuki Nojima;Taka-aki Ishibashi;Shinichi Enami;and Tetsuya Hama
脂肪酸表面活性剂（覆盖大气液态气溶胶的表面，并在海洋中发现）的紫外线（UV）光解作用最近被认为是对流层中羟基（OH）自由基的来源。我们用激光诱导荧光直接观察OH自由基解吸净液体NA作为一个主要的光产物后，213 nm照射的表面。OH自由基脱附的光反应截面上限为9.0（4.1）× 10 ~（-22）cm ~ 2，仅为气相乙酸单体光解反应截面的1.2 ± 0.8%。液体NA的振动和频产生光谱揭示了在液体表面的NA分子的氢键，环状，二聚体结构。这种二聚作用可以抑制OH自由基的形成，导致目前液体NA的光化学反应活性较低。
Ultraviolet (UV) photolysis of fatty acid surfactants─which cover the surfaces of atmospheric liquid aerosols and are found in the oceans─such as nonanoic acid (NA) has recently been suggested as a source of hydroxyl (OH) radicals in the troposphere. We used laser-induced fluorescence to directly observe OH radicals desorbed from the surface of neat liquid NA as a primary photoproduct following 213 nm irradiation. The upper limit of photoreaction cross section for the OH radical desorption was estimated to be 9.0(4.1) × 10–22cm2, which is only 1.2 ± 0.8% of the photoreaction cross section established for the photolysis of gas-phase acetic acid monomers. Vibrational sum-frequency generation spectroscopy for liquid NA revealed the hydrogen-bonded, cyclic, dimer structure of the NA molecules at the liquid surface. This dimerization can inhibit the formation of OH radicals and lead the present low photochemical reactivity of liquid NA.