Free radical formation in supercritical CO2, using muonium as a probe and implication for H atom reaction with ethene.

This report presents the first observation of an alkyl radical in supercritical CO(2) by any magnetic resonance technique. Muoniated ethyl radical has been detected in muon-irradiated supercritical CO(2) solutions. In the presence of a low concentration of ethene in supercritical CO(2), it is found that the addition of muonium to ethene is the only reaction channel, and that the yield of this process is enhanced compared to conventional solvents. The temperature dependence of the hyperfine coupling constants of the ethyl radical suggests that at a density of 0.3 g/cm(3) both the rotational motion of the methyl group and the electronic structure of the radical are similar to those in the gas phase, and therefore that the local environment around the ethyl radical is similar to the gas phase under these conditions. At higher densities, however, there is a remarkable and unexpected density dependence of the hyperfine coupling constant of the ethyl radical, which has never been observed in any environment. In this regime, the density dependence suggests that supercritical CO(2) has a significant effect on the electronic structure of the free radical. Thus, changing the density of CO(2) offers a possible means of tuning the radical reactivity. In addition, at a density of close to 0.4 g/cm(3), CO(2) molecules cluster around the ethyl radical, and this increases the local density around the ethyl radical by a factor of ~1.5.

Monitoring rainwater and seaweed reveals the presence of (131)I in southwest and central British Columbia, Canada following the Fukushima nuclear accident in Japan.

Detailed analysis of (131)I levels in rainwater and in three species of seaweed (Fucus distichus Linnaeus, Macrocystis pyrifera, and Pyropia fallax) collected in southwest British Columbia and Bella Bella, B.C., Canada was performed using gamma-ray spectroscopy following the Fukushima nuclear power plant accident on March 11, 2011. Maximum (131)I activity was found to be 5.8(7) Bq/L in rainwater collected at the campus of Simon Fraser University in Burnaby, B.C. nine days after the accident. Concomitantly, maximum observed activity in the brown seaweed F. distichus Linnaeus was observed to be 130(7) Bq/kg dry weight in samples collected in North Vancouver 11 days following the accident and 67(6) Bq/kg dry weight in samples collected from the Bamfield Marine Sciences Centre on Vancouver Island 17 days following the accident. The (131)I activity in seaweed samples collected in southwest B.C. following the Fukushima accident was an order of magnitude less than what was observed following Chernobyl. Iodine-131 activity in F. distichus Linnaeus remained detectable for 60 days following the accident and was detectable in each seaweed species collected. The Germanium Detector for Elemental Analysis and Radioactivity Studies (GEARS) was modeled using the Geant4 software package and developed as an analytical tool by the Nuclear Science group in the Simon Fraser University Department of Chemistry for the purpose of these measurements.

Generation and detection of the cyclohexadienyl radical in phosphonium ionic liquids.

The formation of the cyclohexadienyl radical, C(6)H(6)Mu, in ionic and molecular solvents has been compared. This is the first time that a muoniated free radical is reported in an ionic liquid. In marked contrast to molecular liquids, free radical generation in ionic liquids is significantly enhanced. Comparison of the hyperfine interactions in the ionic liquid and in molecular solvents and with theoretical calculations, suggests significant and unforeseen solvent interaction with the cyclohexadienyl radical.