HCHO 的光物理氧化产生 HO2 自由基
Nature Chemistry
(
IF
20.2
)
Pub Date : 2023-07-06
, DOI:
10.1038/s41557-023-01272-4
Blair A Welsh
1,
2
,
Maggie E Corrigan
3
,
Emmanuel Assaf
4,
5,
6
,
Klaas Nauta
1
,
Paolo Sebastianelli
1,
7
,
Meredith J T Jordan
3
,
Christa Fittschen
4
,
Scott H Kable
1
Affiliation
School of Chemistry, University of New South Wales, Kensington, New South Wales, Australia.
Combustion Research Facility, Sandia National Laboratories, Livermore, CA, USA.
School of Chemistry, University of Sydney, Sydney, New South Wales, Australia.
Université Lille, CNRS, UMR 8522, PC2A-Physicochimie des Processus de Combustion et de l'Atmosphère, Lille, France.
Chemical Sciences Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO, USA.
Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA.
School of Earth, Atmospheric and Life Sciences, University of Wollongong, Wollongong, New South Wales, Australia.
甲醛 (HCHO) 是大气中含量最高的羰基化合物。它吸收波长小于330 nm的阳光并光解形成H和HCO自由基，然后与O 2反应形成HO 2。在这里，我们证明 HCHO 具有额外的 HO 2形成途径。在光解能量低于自由基形成的能量阈值时，我们通过腔衰荡光谱直接检测低压下的HO 2 ，并通过傅里叶变换红外光谱最终产物分析间接检测1巴下的HO 2 。在电子结构理论和主方程模拟的支持下，我们将这种 HO 2归因于光物理氧化 (PPO)：光激发的 HCHO 非辐射弛豫到基电子态，其中远离平衡、振动激活的 HCHO 分子与热 O 2 发生反应。PPO 可能是对流层化学中的一般机制，并且与光解不同，PPO 将随着O 2压力的增加而增加。
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Photophysical oxidation of HCHO produces HO2 radicals
Formaldehyde, HCHO, is the highest-volume carbonyl in the atmosphere. It absorbs sunlight at wavelengths shorter than 330 nm and photolyses to form H and HCO radicals, which then react with O2 to form HO2. Here we show HCHO has an additional HO2 formation pathway. At photolysis energies below the energetic threshold for radical formation we directly detect HO2 at low pressures by cavity ring-down spectroscopy and indirectly detect HO2 at 1 bar by Fourier-transform infrared spectroscopy end-product analysis. Supported by electronic structure theory and master equation simulations, we attribute this HO2 to photophysical oxidation (PPO): photoexcited HCHO relaxes non-radiatively to the ground electronic state where the far-from-equilibrium, vibrationally activated HCHO molecules react with thermal O2. PPO is likely to be a general mechanism in tropospheric chemistry and, unlike photolysis, PPO will increase with increasing O2 pressure.
更新日期：2023-07-06