ALBERT

Description: Rate constants for the dissociation of highly vibrationally excited ketene (CH(2)CO) have been measured at the threshold for the production of CH(2)((3)B(1)) and CO((1)Sigma(+)). The rate constant increases in a stepwise manner with increasing energy, consistent with the long-standing premise that the rate of a unimolecular reaction is controlled by flux through quantized transition-state thresholds. The data give the energies of the torsional and C-C-O bending vibrations of the transition state.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lovejoy, E R -- Kim, S K -- Moore, C B -- New York, N.Y. -- Science. 1992 Jun 12;256(5063):1541-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17836322" target="_blank"〉PubMed〈/a〉

Description: Atmospheric aerosols exert an important influence on climate through their effects on stratiform cloud albedo and lifetime and the invigoration of convective storms. Model calculations suggest that almost half of the global cloud condensation nuclei in the atmospheric boundary layer may originate from the nucleation of aerosols from trace condensable vapours, although the sensitivity of the number of cloud condensation nuclei to changes of nucleation rate may be small. Despite extensive research, fundamental questions remain about the nucleation rate of sulphuric acid particles and the mechanisms responsible, including the roles of galactic cosmic rays and other chemical species such as ammonia. Here we present the first results from the CLOUD experiment at CERN. We find that atmospherically relevant ammonia mixing ratios of 100 parts per trillion by volume, or less, increase the nucleation rate of sulphuric acid particles more than 100-1,000-fold. Time-resolved molecular measurements reveal that nucleation proceeds by a base-stabilization mechanism involving the stepwise accretion of ammonia molecules. Ions increase the nucleation rate by an additional factor of between two and more than ten at ground-level galactic-cosmic-ray intensities, provided that the nucleation rate lies below the limiting ion-pair production rate. We find that ion-induced binary nucleation of H(2)SO(4)-H(2)O can occur in the mid-troposphere but is negligible in the boundary layer. However, even with the large enhancements in rate due to ammonia and ions, atmospheric concentrations of ammonia and sulphuric acid are insufficient to account for observed boundary-layer nucleation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kirkby, Jasper -- Curtius, Joachim -- Almeida, Joao -- Dunne, Eimear -- Duplissy, Jonathan -- Ehrhart, Sebastian -- Franchin, Alessandro -- Gagne, Stephanie -- Ickes, Luisa -- Kurten, Andreas -- Kupc, Agnieszka -- Metzger, Axel -- Riccobono, Francesco -- Rondo, Linda -- Schobesberger, Siegfried -- Tsagkogeorgas, Georgios -- Wimmer, Daniela -- Amorim, Antonio -- Bianchi, Federico -- Breitenlechner, Martin -- David, Andre -- Dommen, Josef -- Downard, Andrew -- Ehn, Mikael -- Flagan, Richard C -- Haider, Stefan -- Hansel, Armin -- Hauser, Daniel -- Jud, Werner -- Junninen, Heikki -- Kreissl, Fabian -- Kvashin, Alexander -- Laaksonen, Ari -- Lehtipalo, Katrianne -- Lima, Jorge -- Lovejoy, Edward R -- Makhmutov, Vladimir -- Mathot, Serge -- Mikkila, Jyri -- Minginette, Pierre -- Mogo, Sandra -- Nieminen, Tuomo -- Onnela, Antti -- Pereira, Paulo -- Petaja, Tuukka -- Schnitzhofer, Ralf -- Seinfeld, John H -- Sipila, Mikko -- Stozhkov, Yuri -- Stratmann, Frank -- Tome, Antonio -- Vanhanen, Joonas -- Viisanen, Yrjo -- Vrtala, Aron -- Wagner, Paul E -- Walther, Hansueli -- Weingartner, Ernest -- Wex, Heike -- Winkler, Paul M -- Carslaw, Kenneth S -- Worsnop, Douglas R -- Baltensperger, Urs -- Kulmala, Markku -- 227463/European Research Council/International -- England -- Nature. 2011 Aug 24;476(7361):429-33. doi: 10.1038/nature10343.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉CERN, CH-1211 Geneva, Switzerland. jasper.kirkby@cern.ch〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21866156" target="_blank"〉PubMed〈/a〉

Description: The measured reaction probability, gamma for the reaction of chlorine nitrate (CIONa(2)) with 60 percent (by weight) sulfuric acid aerosol increases monotonically with particle size at 250 kelvin. The reacto-diffusive length (l, the effective liquid depth over which reaction occurs) derived from these experiments is 0.037 +/- 0.007 micrometer (95 percent confidence level for precision). The reaction probability for the reaction of CIONO(2) with 60 percent sulfuric acid aerosol doped with approximately 7 x 10(-4) M hydrochloric acid at 250 kelvin is larger by about a factor of 4 than in the absence of hydrochloric acid and varies less with particle size (l = 0.009 +/- 0.005 micrometer). These results provide a test of the theory for gas-particle reactions and further insight into the reactivity of atmospheric aerosol.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hanson, D R -- Lovejoy, E R -- New York, N.Y. -- Science. 1995 Mar 3;267(5202):1326-8.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17812605" target="_blank"〉PubMed〈/a〉