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Sato K.,Japan National Institute of Environmental Studies | Takami A.,Japan National Institute of Environmental Studies | Kato Y.,Japan National Institute of Environmental Studies | Kato Y.,Nuclear Material Control Center | And 5 more authors.
Atmospheric Chemistry and Physics | Year: 2012

Oxygenated organic aerosol (OOA) observed in remote areas is believed to comprise aged secondary organic aerosol (SOA); however, the reaction processes relevant to SOA chemical aging have hitherto been unclear. We recently measured the mass spectra of SOA formed from the photooxidation of aromatic hydrocarbons using an Aerodyne aerosol mass spectrometer (AMS) and reported that SOA aging is slowed with increasing number of alkyl groups in the precursor molecule. In this study, we selected benzene and 1,3,5-trimethylbenzene (TMB) as precursors to analyze SOA formed from the photooxidation of aromatic hydrocarbons in the presence of NO x using high-resolution time-of-flight AMS (H-ToF-AMS) and liquid chromatography/time-of-flight mass spectrometry (LC/TOF-MS). A van Krevelen diagram was studied using the O/C and H/C ratios obtained by H-ToF-AMS for organics present in SOA. The results showed these organics to be rich in carboxylic acids or hydroxycarbonyls and the O/C ratio of SOA formed by the reaction of 1,3,5-TMB to be lower than that for benzene. Analytical results from LC/TOF-MS showed the particulate products formed by the reaction of 1,3,5-TMB to be richer in ketocarboxylic acids than for benzene. These results indicate that SOA aging proceeds mainly by formation of carboxylic acids and that the rate of SOA aging in laboratory chambers is limited by the oxidation of ketone groups. SOA formed in laboratory chamber experiments is less oxidized than for ambient OOA, not only because the experimental duration is insufficient or the SOA mass loading in the chamber is higher than that of the atmosphere. The laboratory chamber experiments under dry conditions are not able to simulate ketocarboxylic acid photochemical oxidation in the aqueous phase. The fractions of organic peroxides to the total SOA mass were determined by iodometric spectrophotometry to be 12 ± 8% (1,3,5-TMB) and <39% (benzene). Further, it was newly found that, unlike the reaction of benzene, only very small amounts of nitrophenols are produced by the reaction of 1,3,5-TMB. © 2012 Author(s).

Raptis K.,International Atomic Energy Agency | Duhamel G.,International Atomic Energy Agency | Ludwig R.,International Atomic Energy Agency | Balsley S.,International Atomic Energy Agency | And 8 more authors.
Journal of Radioanalytical and Nuclear Chemistry | Year: 2013

The on-site laboratory (OSL) at Rokkasho Reprocessing Plant (RRP) is jointly operated by the Japanese authority Nuclear Material Control Centre and the International Atomic Energy Agency (IAEA) and provides, together with the Nuclear Material Laboratory (NML) at Seibersdorf, analytical services to the IAEA's inspectorate. OSL deals with a variety of samples typical to a reprocessing plant including pure product solutions of uranium and plutonium but also mixed U/Pu solutions originating from various stages of the chemical process. For a significant proportion of the samples, the requirement on measurement accuracy and precision from the Inspectorate makes the use of thermal ionization mass spectrometry (TIMS) indispensible. Until recently, all samples intended for TIMS had to undergo time-consuming U/Pu separation before isotope dilution measurement. The need for rapid reporting of analytical results for certain safeguards samples evoked the idea of performing TIMS measurements without prior U/Pu separation for mixed U/Pu products as they are obtained from the PUREX process at RRP. For this purpose, a systematic study was initiated to probe the figure of merits and limitations of conducting TIMS analyses on mixed U/Pu samples and, in particular, whether the accuracy and precision of the main ratios of interest, n(235U)/n(238U) and n(240Pu)/n(239Pu), are influenced by the presence of larger amounts of the other element. A series of synthetic mixtures with U/Pu ratios ranging from 1:10 up to 100:1 were prepared and measured in both laboratories-OSL and NML-using ThermoFisher TRITON multi-collector TIMS instruments. For the n(235U)/ n(238U) ratio, interference due to 238Pu was observed which can be significant depending on the U/Pu ratio and the 238Pu abundance. However, for the n(240Pu)/n(239Pu) ratio, which is of premier importance for safeguarding RRP, no significant interference arising from the concomitant U was detected independently of enrichment. Even in samples with an excess of U (U/Pu ratio of 100:1), compliance with International Target Values (ITV2010) was demonstrated for n(240Pu)/n(239Pu) results with a relative difference to certified not exceeding 0.01 %. © Akadémiai Kiadó, Budapest, Hungary 2012.

Kanda T.,Tokyo University of Science | Kato Y.,Tokyo University of Science | Kato Y.,Nuclear Material Control Center | Imai T.,Tokyo University of Science | Tsukiyama K.,Tokyo University of Science
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms | Year: 2011

Irradiation of IR Free Electron Laser at Tokyo University of Science (FEL-TUS) to t-butyl isonitrile ((CH 3) 3C-N≡C) in the gas phase induced the isomerization reaction to trimethylacetonitrile ((CH 3) 3C-C≡N). From the kinetic analyses, the isomerization reaction was attributed to the IR multiphoton activated unimolecular process. The wide frequency tunability of FEL-TUS enabled us to reveal that the excitation of the -N≡C as well as the C-N stretching motion efficiently drove the isomerization. © 2011 Elsevier B.V. All rights reserved.

Miyamoto Y.,Osaka University | Majima T.,Osaka University | Arai S.,Hill Research | Katsumata K.,Global Environmental Forum | And 7 more authors.
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms | Year: 2011

The irradiation of a free electron laser at Tokyo University of Science (FEL-TUS) to β-propiolactone molecules in the gas phase has efficiently induced the infrared multiple photon dissociation of the compound in the wavenumber regions of 1000-1100 and 1700-2000 cm-1. The products were carbon dioxide and ethylene at equal amounts, where carbon dioxide was enriched with 13C under selected irradiation conditions. The relative yields of products and the selectivity of 13C were examined under various experimental conditions; the maximum 13C atom fraction of 59% was achieved when 2.5 Torr β-propiolactone was irradiated by FEL pulses at 1750 cm-1 with a fluence of 5.8 J cm-2. One of the reasons of this high selectivity is a large isotope shift of ∼47 cm-1 for the CO stretching vibration around 1880 cm-1, which is larger than the energy resolution of FEL-TUS. Another possible factor may be a shorter micropulse interval (∼350 ps) of FEL-TUS than the collisional frequency of β-propiolactone molecules in the gas phase, which prevents the collisional energy transfer from 13C molecules to 12C molecules during successive micropulses. © 2010 Elsevier B.V. All rights reserved.

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