[ { "id": "authors:5hdt0-kgf30", "collection": "authors", "collection_id": "5hdt0-kgf30", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20191218-140316314", "type": "conference_item", "title": "Reactions of atmospheric peroxy radicals studied by synchrotron VUV multiplexed photoionization mass spectrometry", "author": [ { "family_name": "Dodson", "given_name": "Leah G.", "orcid": "0000-0001-5960-056X", "clpid": "Dodson-Leah-G" }, { "family_name": "Shen", "given_name": "Linhan", "orcid": "0000-0003-3871-655X", "clpid": "Shen-Linhan" }, { "family_name": "Savee", "given_name": "John", "orcid": "0000-0002-6881-935X", "clpid": "Savee-John-D" }, { "family_name": "Osborn", "given_name": "David L.", "orcid": "0000-0003-4304-8218", "clpid": "Osborn-David-L" }, { "family_name": "Eddingsaas", "given_name": "Nathan C.", "orcid": "0000-0003-1539-5415", "clpid": "Eddingsaas-Nathan-C" }, { "family_name": "Sander", "given_name": "Stanley P.", "orcid": "0000-0003-1424-3620", "clpid": "Sander-Stanley-P" }, { "family_name": "Taatjes", "given_name": "Craig A.", "orcid": "0000-0002-9271-0282", "clpid": "Taatjes-Craig-A" }, { "family_name": "Grieman", "given_name": "Fred J.", "orcid": "0000-0002-5995-8286", "clpid": "Grieman-Fred-J" }, { "family_name": "Okumura", "given_name": "Mitchio", "orcid": "0000-0001-6874-1137", "clpid": "Okumura-M" } ], "abstract": "Peroxy radicals are key intermediates in the oxidn. chem. of both anthropogenic and biogenic Volatile Org. Compds.(VOCs) in the troposphere. These species are central in the formation of photochem. smog and org. aerosols, and can be formed from abstraction reactions or from addn. reactions with unsatd. hydrocarbons. Lab. studies of the kinetics of peroxy radical reactions are complicated by the many competing self- and cross-reactions that typically occur. The large no. of possible products, esp. chain-propagating radical channels, further complicates the chem. Here we describe recent expts. using time-resolved photoionization mass spectrometry (PIMS) with ionization by VUV synchrotron radiation. This method provides a powerful, highly sensitive technique for studying the product branching ratios and reaction rates, by selective time-resolved detection of many of the reactants, intermediates, and primary products. We report investigations of peroxy radical reactions in a laser-photolysis low-pressure flow cell expt. that utilizes tunable VUV radiation generated at the Advanced Light Source synchrotron at the Lawrence Berkeley Lab., coupled to the Sandia multiplexed PIMS app. We have performed expts. on the reactions of the acetyl peroxy radicals, as well as the selfreaction of the Et peroxy radical. We are able to det. relative product yields based on measurements of abs. radical concns., new abs. photoionization cross sections, with the aid of kinetic modeling.", "publisher": "Caltech Library", "publication_date": "2015-03" }, { "id": "authors:3cy4y-e2p54", "collection": "authors", "collection_id": "3cy4y-e2p54", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150219-145521644", "type": "article", "title": "VUV Photoionization Cross Sections of HO\u2082, H\u2082O\u2082, and H\u2082CO", "author": [ { "family_name": "Dodson", "given_name": "Leah G.", "orcid": "0000-0001-5960-056X", "clpid": "Dodson-Leah-G" }, { "family_name": "Shen", "given_name": "Linhan", "orcid": "0000-0003-3871-655X", "clpid": "Shen-Linhan" }, { "family_name": "Savee", "given_name": "John D.", "orcid": "0000-0002-6881-935X", "clpid": "Savee-John-D" }, { "family_name": "Eddingsaas", "given_name": "Nathan C.", "orcid": "0000-0003-1539-5415", "clpid": "Eddingsaas-Nathan-C" }, { "family_name": "Welz", "given_name": "Oliver", "clpid": "Welz-Oliver" }, { "family_name": "Taatjes", "given_name": "Craig A.", "orcid": "0000-0002-9271-0282", "clpid": "Taatjes-Craig-A" }, { "family_name": "Osborn", "given_name": "David L.", "orcid": "0000-0003-4304-8218", "clpid": "Osborn-David-L" }, { "family_name": "Sander", "given_name": "Stanley P.", "orcid": "0000-0003-1424-3620", "clpid": "Sander-Stanley-P" }, { "family_name": "Okumura", "given_name": "Mitchio", "orcid": "0000-0001-6874-1137", "clpid": "Okumura-M" } ], "abstract": "The absolute vacuum ultraviolet (VUV) photoionization spectra of the hydroperoxyl radical (HO\u2082), hydrogen peroxide (H\u2082O\u2082), and formaldehyde (H_2CO) have been measured from their first ionization thresholds to 12.008 eV. HO\u2082, H\u2082O\u2082, and H\u2082CO were generated from the oxidation of methanol initiated by pulsed-laser-photolysis of Cl\u2082 in a low-pressure slow flow reactor. Reactants, intermediates, and products were detected by time-resolved multiplexed synchrotron photoionization mass spectrometry. Absolute concentrations were obtained from the time-dependent photoion signals by modeling the kinetics of the methanol oxidation chemistry. Photoionization cross sections were determined at several photon energies relative to the cross section of methanol, which was in turn determined relative to that of propene. These measurements were used to place relative photoionization spectra of HO\u2082, H\u2082O\u2082, and H\u2082CO on an absolute scale, resulting in absolute photoionization spectra.", "doi": "10.1021/jp508942a", "issn": "1089-5639", "publisher": "American Chemical Society", "publication": "Journal of Physical Chemistry A", "publication_date": "2015-02-26", "series_number": "8", "volume": "119", "issue": "8", "pages": "1279-1291" }, { "id": "authors:j2n0h-c3z86", "collection": "authors", "collection_id": "j2n0h-c3z86", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140811-133255291", "type": "conference_item", "title": "Kinetics and near-infrared spectroscopy of chlorine-substituted peroxy radicals", "author": [ { "family_name": "Smarte", "given_name": "Matthew D.", "orcid": "0000-0002-4835-7880", "clpid": "Smarte-Matthew-D" }, { "family_name": "Dodson", "given_name": "Leah G.", "orcid": "0000-0001-5960-056X", "clpid": "Dodson-Leah-G" }, { "family_name": "Takematsu", "given_name": "Kana", "orcid": "0000-0002-2334-336X", "clpid": "Takematsu-Kana" }, { "family_name": "Eddingsaas", "given_name": "Nathan C.", "orcid": "0000-0003-1539-5415", "clpid": "Eddingsaas-Nathan-C" }, { "family_name": "Okumura", "given_name": "Mitchio", "orcid": "0000-0001-6874-1137", "clpid": "Okumura-M" } ], "abstract": "Peroxy radicals form in the atm. oxidn. of nearly every volatile org. compd. (VOC). Their competing fates propagate or terminate free radical chem. in the troposphere. Atomic chlorine is a minor tropospheric oxidant, found in marine and coastal regions, which reacts with volatile alkenes to yield chlorine-substituted peroxy radicals. In this work, we present the near-IR absorption spectra of peroxy radicals formed in the chorine-initiated oxidn. of a variety of VOCs including isoprene, the most important nonmethane hydrocarbon emitted into the troposphere. We use cavity ringdown spectroscopy to observe the weak A-X electronic transition of peroxy radicals in the near-IR region. By monitoring the temporal decay of absorption features under varying radical environments, we report rate consts. for the self reaction of chlorine-substituted peroxy radicals as well as their dominant atm. fates: reaction with HO\u2082 and NO. Reaction with HO\u2082 is important in pristine environments while reaction with NO dominates in polluted regions. We compare our results to those available for hydroxyl-substituted and alkyl peroxy radicals to elucidate the effect of chlorine substitution on peroxy radical reactivity. To our knowledge, these results report the first near-IR absorption spectrum of a peroxy radical derived from isoprene oxidn. The real-time kinetic measurements of the reaction with HO\u2082 and NO provide insight into the highly atmospherically relevant isoprene system.", "publisher": "Caltech Library", "publication_date": "2014-08" }, { "id": "authors:5d7bt-hp887", "collection": "authors", "collection_id": "5d7bt-hp887", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140423-074008314", "type": "conference_item", "title": "Spectroscopy and kinetics of the peroxy radicals formed by chlorine-initiated oxidation of isoprene", "author": [ { "family_name": "Dodson", "given_name": "Leah G.", "orcid": "0000-0001-5960-056X", "clpid": "Dodson-Leah-G" }, { "family_name": "Smarte", "given_name": "Matthew D.", "orcid": "0000-0002-4835-7880", "clpid": "Smarte-Matthew-D" }, { "family_name": "Takematsu", "given_name": "Kana", "orcid": "0000-0002-2334-336X", "clpid": "Takematsu-Kana" }, { "family_name": "Eddingsaas", "given_name": "Nathan C.", "orcid": "0000-0003-1539-5415", "clpid": "Eddingsaas-Nathan-C" }, { "family_name": "Okumura", "given_name": "Mitchio", "orcid": "0000-0001-6874-1137", "clpid": "Okumura-M" } ], "abstract": "Peroxy radicals dominate atm. chem. as important reaction intermediates in the oxidn. of volatile org. compds. (VOCs).\nBiogenic alkene emissions such as isoprene and 2-methyl-3-buten-2-ol (MBO-232) react rapidly with free radicals to form \u03b2-substituted alkylperoxy radicals. Chlorine-initiated oxidn. of VOCs has recently become of interest as more in-land sources\nof chlorine atoms are discovered. We have directly detected the A-X electronic transition spectrum of chlorine-substituted\natmospherically-relevant alkyl peroxy radicals from 7000-9000 cm\u207b\u00b9 using cavity ringdown spectroscopy. Spectra of peroxy radicals formed by chlorine-initiated oxidn. of isoprene, 2-butene, 3-methyl-1-butene, and MBO-232 are presented here. Kinetic rate consts. of peroxy radical self-reactions and peroxy radical reactions with HO\u2082 and NO were obtained by directly observing the near-IR absorption spectrum of the peroxy radical intermediate. These rate consts. will be reported here.", "publisher": "Caltech Library", "publication_date": "2014-03" }, { "id": "authors:dqy6b-9gg45", "collection": "authors", "collection_id": "dqy6b-9gg45", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140429-131752018", "type": "conference_item", "title": "Kinetics and product yields of the acetyl peroxy + HO\u2082 radical reaction studied by photoionization mass spectrometry", "author": [ { "family_name": "Dodson", "given_name": "Leah G.", "orcid": "0000-0001-5960-056X", "clpid": "Dodson-Leah-G" }, { "family_name": "Shen", "given_name": "Linhan", "orcid": "0000-0003-3871-655X", "clpid": "Shen-Linhan" }, { "family_name": "Savee", "given_name": "John D.", "orcid": "0000-0002-6881-935X", "clpid": "Savee-John-D" }, { "family_name": "Eddingsaas", "given_name": "Nathan C.", "orcid": "0000-0003-1539-5415", "clpid": "Eddingsaas-Nathan-C" }, { "family_name": "Welz", "given_name": "Oliver", "clpid": "Welz-Oliver" }, { "family_name": "Taatjes", "given_name": "Craig A.", "orcid": "0000-0002-9271-0282", "clpid": "Taatjes-Craig-A" }, { "family_name": "Osborn", "given_name": "David L.", "orcid": "0000-0003-4304-8218", "clpid": "Osborn-David-L" }, { "family_name": "Sander", "given_name": "Stanley P.", "orcid": "0000-0003-1424-3620", "clpid": "Sander-Stanley-P" }, { "family_name": "Okumura", "given_name": "Mitchio", "orcid": "0000-0001-6874-1137", "clpid": "Okumura-M" } ], "abstract": "The acetyl peroxy radical (CH\u2083C(O)O\u2082) is a key intermediate in the oxidn. of carbonyl-contg. hydrocarbons in\nthe troposphere. Reaction of acetyl peroxy radicals with HO\u2082 has been suggested as a source of OH radicals\nin low-NO\u2093 conditions. Previous work on this reaction obsd. only two product channels forming (1) peracetic\nacid and (2) acetic acid. Recent expts. have shown that there is a third channel that generates the radicals OH\nand acetoxy: CH\u2083C(O)O\u2082 + HO\u2082 \u2192 (1) CH\u2083C(O)OOH + O\u2082 (2) CH\u2083C(O)OH + O\u2083 (3) CH\u2083C(O)O + O\u2082 + OH\nThis last pathway to OH formation would then contribute to the apparent isoprene OH recycling suggested by\ndiscrepancies between atm. models and field observations of OH. There have, however, been significant\ndisagreements among expts. on the yield of OH in this reaction. We report our preliminary studies of acetyl\nperoxy reaction with itself and HO\u2082. Expts. were conducted at the Advanced Light Source synchrotron at the\nLawerence Berkeley National Lab. using tunable VUV ionizing radiation coupled to the Sandia National Lab.\npulsed-laser-photolysis multiplexed photoionization mass spectrometer to detect time-resolved photofragmets of\nreactants, intermediates, and products. From these results, we report new values for the branching fractions of\nthe three product channels in the acetyl peroxy + HO\u2082 radical reaction.", "publisher": "Caltech Library", "publication_date": "2014-03" } ]