Measuring Photodissociation Product Quantum Yields Using Chemical Ionization Mass Spectrometry: A Case Study with Ketones.

Autor: Link MF; Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States., Farmer DK; Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States., Berg T; Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States., Flocke F; National Center for Atmospheric Research, Boulder, Colorado 80301, United States., Ravishankara AR; Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States.; Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado 80523, United States.
Jazyk: angličtina
Zdroj: The journal of physical chemistry. A [J Phys Chem A] 2021 Aug 12; Vol. 125 (31), pp. 6836-6844. Date of Electronic Publication: 2021 Jul 29.
DOI: 10.1021/acs.jpca.1c03140
Abstrakt: 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)O 2 ) 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)O 2 and associated photolysis processes.
Databáze: MEDLINE
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