A search for a heavy right-handed WR boson, and heavy right-handed neutrinos Nl (ℓ = e, μ) performed by the CMS experiment is summarized here. Using the 2.6 fb–1 of integrated luminosity recorded by ...the CMS experiment in 2015 at a center-of-mass energy of 13 TeV, this search seeks evidence of a WR boson and Nl neutrinos in events with two leptons and two jets. The data do not significantly exceed expected backgrounds, and are consistent with expected results of the Standard Theory given uncertainties. For Standard Theory extensions with strict left-right symmetry, and assuming only one Nl flavor contributes significantly to the WR decay width, mass limits are set in the two-dimensional (MWR, MNl) plane at 95% confidence level. The limits extend to a WR mass of 3.3 TeV in the electron channel and 3.5 TeV in the muon channel, and span a wide range of Nl masses below MWR.
Secondary organic aerosol (SOA) particles result from the condensation of oxidized volatile organic compounds (VOC) and consist of a complex mixture that is not conducive to complete compositional ...analysis. We present a simple methodology for determining the quantities of aldehydes and ketones, alcohols, and carboxylic acids in such samples via derivatization and high-performance liquid chromatography (HPLC) with ultraviolet–visible absorption detection and tandem mass spectrometry (MS/MS). Useful concentration ranges are presented with an examination of the specificity of these compounds in multiply substituted systems. Such data are valuable in modeling the formation of laboratory-generated aerosols and in identifying point sources of field-collected aerosol samples. Calibration curves on standard samples, MS/MS transitions, including collisionally induced dissociation (CID) products, and a quantitative examination of the specificity of the derivatization reagents toward multiple functional groups are presented for a series of aliphatic standard samples. These methods are then applied to filter extracts from SOA derived from 1-iodooctane photolysis at 254 nm to demonstrate the methodology on a complex system. Ultimately, this methodology enables the measurement of variations in the chemical nature of the oxygen within an SOA particle, providing a distribution of functional group concentrations.
Alkylperoxy Radical Photochemistry in Organic Aerosol Formation Processes Kalafut-Pettibone, Alicia J; Klems, Joseph P; Burgess, Donald R ...
The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory,
12/2013, Letnik:
117, Številka:
51
Journal Article
Recenzirano
Recent studies have shown that 254 nm light can be used to generate organic aerosol from iodoalkane/air mixtures via photodissociation of the C–I bond and subsequent oxidation of the alkyl radical. ...We examine organic aerosol formed from the 1-iodooctane photolysis at this wavelength using high-performance liquid chromatography (HPLC) with derivatization to selectively probe carbonyl- and hydroxyl-containing molecules. Tandem mass spectrometry reveals that the product distributions are much more complex than a traditional low-NO x peroxy–peroxy oxidation mechanism from a single parent isomer would justify. We propose that this difference is due to peroxy radical photochemistry, leading to two major channels: direct peroxy radical isomerization via internal H-abstraction and reverse dissociation to form alkyl radical and O2. The complexity of the product spectrum is derived from both scrambling of the radical site in the alkyl radical and the additional oxidation of otherwise stable peroxy radicals as a result of the isomerization. A branching ratio for these channels is estimated using a canonical representation of the internal energy distribution. Lifetime estimates using extrapolated ethyl peroxy absorption cross sections and the actinic flux near 310 nm show that peroxy radical photochemistry may play a role in defining the composition of atmospheric secondary organic aerosol formed in pristine (low-NO x ) environments.
