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Title:HIGH RESOLUTION MICROWAVE SPECTROSCOPY IN A CRYOGENIC BUFFER GAS CELL: BRANCHING RATIOS AND REACTIVE INTERMEDIATES IN THE OZONOLYSIS OF ISOPRENE
Author(s):Porterfield, Jessie P.
Contributor(s):McCarthy, Michael C.; Patterson, David; Eibenberger, Sandra
Subject(s):Atmospheric science
Abstract:A new method to quantify reaction product ratios using high resolution microwave spectroscopy in a cryogenic buffer gas cell has been developed. We demonstrate its power with product ratio quantification in the ozonolysis of isoprene, \ce{CH2=C(CH3)-CH=CH2}, the most abundant, non-methane hydrocarbon emitted into the atmosphere by vegetation. Purified \ce{O3} and isoprene were mixed for approximately 10\,s under dilute (1.5-4\% in argon) continuous flow conditions in an alumina tube held at 298 K and 5 Torr. Products exiting the tube were rapidly slowed and cooled within the buffer gas cell by collisions with cryogenic (4-7\,K) He. High resolution chirped pulse microwave detection between 12 and 26\,GHz was used to achieve isomer-specific product quantification with ppb sensitivity. \begin{wrapfigure}{r}{0pt} \includegraphics[scale=0.59]{graphical_abstract_ISMS.eps} \end{wrapfigure} We determined a ratio of MACR to MVK of 2.1 $\pm$ 0.4 under 1:1 ozone to isoprene conditions and 2.1 $\pm$ 0.2 under 2:1 ozone to isoprene conditions, a finding which is consistent with previous experimental results. The potential to perform a complete branching ratio analysis is discussed using $^{13}$C isotopic substitution of isoprene. We also discuss the prospects for detecting the proposed Criegee intermediates in this reaction, methacrolein-oxide and methyl vinyl ketone-oxide, neither of which have ever been observed.
Issue Date:06/22/18
Publisher:International Symposium on Molecular Spectroscopy
Citation Info:APS
Genre:Conference Paper / Presentation
Type:Text
Language:English
URI:http://hdl.handle.net/2142/100793
DOI:10.15278/isms.2018.FF08
Other Identifier(s):FF08
Date Available in IDEALS:2018-08-17
2018-12-12


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