Measuring Photodissociation Product Quantum Yields Using Chemical Ionization Mass Spectrometry: A Case Study with Ketones
Measuring Photodissociation Product Quantum Yields Using Chemical Ionization Mass Spectrometry: A Case Study with Ketones
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使用化学电离质谱测量光解离产物量子产率：酮的案例研究
DOI：
10.1021/acs.jpca.1c03140
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Ravishankara, A. R.
中科院分区：
文献类型：
--
作者：
Link, Michael F.;Farmer, Delphine K.;Berg, Tyson;Flocke, Frank;Ravishankara, A. R.
光解量子产率的测量具有挑战性，因为测量第一代光解产物、其他产物或污染物的干扰、足够的光子通量和/或光解物的低吸收截面以产生可检测的产物以及光子通量的量化存在困难。在丙酮（和其他与大气相关的酮类）的情况下，光解量子产率的不确定性产生了大气中计算的OH自由基和酰基过氧硝酸盐产量的不确定性。本文提出了一种利用化学电离质谱（CIMS）测定空气中酮类光解产生的酰基过氧自由基（RC(O)O2）来测定光解产物量子产率的新方法。我们的CIMS方法与先前发表的在254 nm光解双乙酰基和甲基乙基酮（MEK）的酰基自由基的量子产率很好地一致。此外，我们通过测量MEK的光解分支比来强调这种CIMS方法的能力。我们建议CIMS的未来应用（在实验室和现场）来测量RC(O) o2和相关的光解过程。
Measurements of photolysis quantum yields are challenging because of the difficulties in measuring the first-generation photodissociation products, interference from other products or contaminants, sufficient photon fluxes and/or low absorption cross sections of the photolyte to make detectable amounts of products, and quantification of the photon flux. In the case of acetone (and other atmospherically relevant ketones) the uncertainty in the photolysis quantum yield creates uncertainty in the calculated OH radical and acyl peroxy nitrate production in the atmosphere. We present a new method for determining photodissociation product quantum yields by measuring acyl peroxy radicals (RC(O)O2) produced in the photolysis of ketones in air using chemical ionization mass spectrometry (CIMS). We show good agreement of our CIMS method with previously published quantum yields of the acyl radical from photolysis of biacetyl and methyl ethyl ketone (MEK) at 254 nm. Additionally, we highlight the capabilities of this CIMS method through the measurement of photolysis branching ratios for MEK. We suggest future applications of CIMS (in the laboratory and field) to measure RC(O)O2and associated photolysis processes.