title: Rate coefficients of C(1) and C(2) Criegee intermediate reactions with formic and acetic Acid near the collision limit: direct kinetics measurements and atmospheric implications.
abstract: Rate coefficients are directly determined for the reactions of the Criegee intermediates (CI) CH2 OO and CH3 CHOO with the two simplest carboxylic acids, formic acid (HCOOH) and acetic acid (CH3 COOH), employing two complementary techniques: multiplexed photoionization mass spectrometry and cavity-enhanced broadband ultraviolet absorption spectroscopy. The measured rate coefficients are in excess of 1×10(-10)  cm(3)  s(-1) , several orders of magnitude larger than those suggested from many previous alkene ozonolysis experiments and assumed in atmospheric modeling studies. These results suggest that the reaction with carboxylic acids is a substantially more important loss process for CIs than is presently assumed. Implementing these rate coefficients in global atmospheric models shows that reactions between CI and organic acids make a substantial contribution to removal of these acids in terrestrial equatorial areas and in other regions where high CI concentrations occur such as high northern latitudes, and implies that sources of acids in these areas are larger than previously recognized.
authors.affiliation: Combustion Research Facility, Sandia National Laboratories, Stop 9055, Livermore, CA 94551-0969 (USA).
authors.forename: Oliver
authors.initials: O
authors.lastname: Welz
authors.forename: Arkke J
authors.initials: AJ
authors.lastname: Eskola
authors.forename: Leonid
authors.initials: L
authors.lastname: Sheps
authors.forename: Brandon
authors.initials: B
authors.lastname: Rotavera
authors.forename: John D
authors.initials: JD
authors.lastname: Savee
authors.forename: Adam M
authors.initials: AM
authors.lastname: Scheer
authors.forename: David L
authors.initials: DL
authors.lastname: Osborn
authors.forename: Douglas
authors.initials: D
authors.lastname: Lowe
authors.forename: A
authors.initials: A
authors.lastname: Murray Booth
authors.forename: Ping
authors.initials: P
authors.lastname: Xiao
authors.forename: M
authors.initials: M
authors.lastname: Anwar H Khan
authors.forename: Carl J
authors.initials: CJ
authors.lastname: Percival
authors.forename: Dudley E
authors.initials: DE
authors.lastname: Shallcross
authors.forename: Craig A
authors.initials: CA
authors.lastname: Taatjes
keywords: Criegee intermediates; atmospheric chemistry; gas-phase chemistry; kinetics; organic acids