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Emissions of nonmethane hydrocarbon compounds to the atmosphere from the biosphere exceed those from anthropogenic activity. Isoprene, a five-carbon diene, contributes more than 40% of these emissions. Once emitted to the atmosphere, isoprene is rapidly oxidized by the hydroxyl radical OH. We report here that under pristine conditions isoprene is oxidized(More)
We describe a nearly explicit chemical mechanism for isoprene photooxidation guided by chamber studies that include time-resolved observation of an extensive suite of volatile compounds. We provide new constraints on the chemistry of the poorly-understood isoprene δ-hydroxy channels, which account for more than one third of the total isoprene carbon flux(More)
Forests emit large quantities of volatile organic compounds (VOCs) to the atmosphere. Their condensable oxidation products can form secondary organic aerosol, a significant and ubiquitous component of atmospheric aerosol, which is known to affect the Earth's radiation balance by scattering solar radiation and by acting as cloud condensation nuclei. The(More)
We report experimental evidence for the formation of C(5)-hydroperoxyaldehydes (HPALDs) from 1,6-H-shift isomerizations in peroxy radicals formed from the hydroxyl radical (OH) oxidation of 2-methyl-1,3-butadiene (isoprene). At 295 K, the isomerization rate of isoprene peroxy radicals (ISO2•) relative to the rate of reaction of ISO2• + HO2 is(More)
Methacryloyl peroxynitrate (MPAN), the acyl peroxynitrate of methacrolein, has been suggested to be an important secondary organic aerosol (SOA) precursor from isoprene oxidation. Yet, the mechanism by which MPAN produces SOA through reaction with the hydroxyl radical (OH) is unclear. We systematically evaluate three proposed mechanisms in controlled(More)
Atmospheric field measurements and models of the stratospheric sulfate aerosol layer led to the suggestion that sulfuric acid (H2SO4) must photolyze at high altitudes. We propose that excitation of vibrational overtones of H2SO4 and its hydrate in the near-infrared and visible leads to photolysis, forming sulfur trioxide (SO3) and water. On the basis of(More)
We have calculated the band profiles of the OH-stretching fundamental and overtone transitions in the proton donor unit of the water dimer complex. We have used a local mode Hamiltonian that includes both OH-stretching and OO-stretching motion but separates these adiabatically. The variation of OH-stretching frequency and anharmonicity with OO displacement(More)
We have calculated the frequencies and intensities of the hydrogen-bonded OH-stretching transitions in the water dimer complex. The potential-energy curve and dipole-moment function are calculated ab initio at the coupled cluster with singles, doubles, and perturbative triples level of theory with correlation-consistent Dunning basis sets. The vibrational(More)
Lipophilic monocations can pass through phospholipid bilayers and accumulate in negatively-charged compartments such as the mitochondrial matrix, driven by the membrane potential. This property is used to visualize mitochondria, to deliver therapeutic molecules to mitochondria and to measure the membrane potential. In theory, lipophilic dications have a(More)