Unexpectedly high concentrations of ultrafine particles were observed over a wide range of latitudes in the upper troposphere and lower stratosphere. Particle number concentrations and size distributions simulated by a numerical model of ion-induced nucleation, constrained by measured thermodynamic data and observed atmospheric key species, were consistent with the observations. These findings indicate that, at typical upper troposphere and lower stratosphere conditions, particles are formed by this nucleation process and grow to measurable sizes with sufficient sun exposure and low preexisting aerosol surface area. Ion-induced nucleation is thus a globally important source of aerosol particles, potentially affecting cloud formation and radiative transfer.

Rate constants for the reactions of Kr+(2P3/2) with HCl and DCl and of Ar+ with HCl have been measured as a function of reactant ion/reactant neutral average center-of-mass kinetic energy (〈KEc.m.〉 ) at several temperatures. The measurements were made using helium as the carrier gas. From these data we have derived the dependences of the rate constants on the rotational temperature of H(D)Cl. Rate constants for the reaction of Kr+(2P1/2) with HCl have also been measured as a function of temperature. The rate constants for all of the reactions were found to decrease with increasing temperature. The rate constants were also found to decrease with increasing 〈KEc.m.〉 at low 〈KEc.m.〉 but then to increase at higher 〈KEc.m.〉 . A significant rotational temperature dependence of the rate constant was derived for the reaction of Kr+(2P3/2) with H(D)Cl. The analogous derivation for Ar+ reacting with HCl showed the rate constant for this reaction to be independent of the rotational temperature of HCl within experimental uncertainty.

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− 10 7 cm −3 and the slopes of Log J vs. Log [H 2 SO 4 ] and Log J vs. Log [TMA] were 4-6 and 1, respectively, strikingly similar to the case of ammonia (NH 3 ) ternary nucleation (Benson et al., 2011). At lower RH, however, enhancement in J due to TMA was up to an order of magnitude greater than that due to NH 3 . These findings imply that both amines and NH 3 are important nucleation species, but under dry atmospheric conditions, amines may have stronger effects on H 2 SO 4 nucleation than NH 3 . Aerosol models should therefore take into account inorganic and organic base compounds together to fully understand the widespread new particle formation events in the lower troposphere.

We have studied the rate constants for the reaction of O ϩ with N 2 over the temperature range 300-1600 K and the reaction of O ϩ with O 2 over the range 300 to 1800 K. The results are in good agreement with previous measurements made up to 900 K. The rate constant for the O ϩ reaction with N 2 shows a minimum in the temperature range 1100-1300 K. The increase above this temperature is due to N 2 vϭ2 becoming populated. The rate constant for O ϩ ϩO 2 shows a minimum in the 800-1100 K range. Comparing to previous drift tube measurements allows the rate constant for O 2 ͑vϾ0͒ to be derived. The vϾ0 rate constant is approximately five times larger than the vϭ0 rate constant.

The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden to Department of Defense, Washington Headquarters Services Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S)AFRL/VSBXT SPONSOR/MONITOR'S REPORT DISTRIBUTIO NIAVAILABILITY STATEMENTApproved for public release; distribution unlimit 2 0 619 3 SUPPLEMENTARY NOTESReprinted from J. Phys. Chem., V. 110, pp. 1491-1499 © 2006, American Chemical Society. *U. of Goettingen, Goettingen, Germany #Inst. for Problems of Chem. Physics, Russian Academy of Sciences, 142432 Chernogolovka, Russia.14. ABSTRACT Statistical adiabatic channel model/classical trajectory (SACM/CT) calculations have been performed for transitional mode dynamics in the simple bond fission reactions of C 6 H 6 + -" C 6 H 5 ' + H and n-C 6 HC 4 H 9 + -C 7 H 7 + + n-C 3 H 7 . Reduced-dimensionality model potentials have been designed to take advantage ofab initio results as far as available. Average anisotropy amplitudes of the potentials were fitted by comparison of calculated specific rate constants k(EJ) with measured values. The kinetic shifts of the calculated (kU) curves and the corresponding bond energies Eo(J=O), derived as 3.90 ± 0.05 eV for C 6 H 6 + and 1.78 ± 0.05 eV for n-C 6 H 5 C 4 H 9 +, were in good agreement with literature values from thermochemical studies. Kinetic shifts from fixed tight activated complex Rice-Ramsperger-Kassel-Marcus (RRKM) theory, which also reproduces the measured k(E), were larger than the present SACM/CT results as well as earlier results from variational transition state theory (for C 6 H-6). The approach using RRKM theory was found to underestimate Eo(J=O) by about 0.2-0.3 eV. A simplified SACM/CT-based method is also proposed which circumvents the trajectory calculations and allows derivation ofEo(J=O) on the basis of measured k(E) and which provides similar accuracy as the full SACM/CT treatment. SUBJECT 0•initio results as far as available. Average anisotropy amplitudes of the potentials were fitted by comparison of calculated specific rate constants k(EJ) with measured values. The kinetic shifts of the calculated k(E) curves and the corresponding bond energies Eo(J=0), derived as 3.90 ± 0.05 eV for C 6 H 6 + and 1.78 ± 0.05 eV for n-C6HsC 4 H 9 +, were in good agreement wi...

[1] On 28 February 2000, a volcanic cloud from Hekla volcano, Iceland, was serendipitously sampled by a DC-8 research aircraft during the SAGE III Ozone Loss and Validation Experiment (SOLVE I). It was encountered at night at 10.4 km above sea level (in the lower stratosphere) and 33-34 hours after emission. The cloud is readily identified by abundant SO 2 ( 1 ppmv), HCl ( 70 ppbv), HF ( 60 ppbv), and particles (which may have included fine silicate ash). We compare observed and modeled cloud compositions to understand its chemical evolution. Abundances of sulfur and halogen species indicate some oxidation of sulfur gases but limited scavenging and removal of halides. Chemical modeling suggests that cloud concentrations of water vapor and nitric acid promoted polar stratospheric cloud (PSC) formation at 201-203 K, yielding ice, nitric acid trihydrate (NAT), sulfuric acid tetrahydrate (SAT), and liquid ternary solution H 2 SO 4 /H 2 O/HNO 3 (STS) particles. We show that these volcanically induced PSCs, especially the ice and NAT particles, activated volcanogenic halogens in the cloud producing >2 ppbv ClO x . This would have destroyed ozone during an earlier period of daylight, consistent with the very low levels of ozone observed. This combination of volcanogenic PSCs and chlorine destroyed ozone at much faster rates than other PSCs that Arctic winter. Elevated levels of HNO 3 and NO y in the cloud can be explained by atmospheric nitrogen fixation in the eruption column due to high temperatures and/or volcanic lightning. However, observed elevated levels of HO x remain unexplained given that the cloud was sampled at night.

Many chemical reactions in atmospheric aerosols and bulk aqueous environments are influenced by the surrounding solvation shell, but the precise molecular interactions underlying such effects have rarely been elucidated. We exploited recent advances in isomer-specific cluster vibrational spectroscopy to explore the fundamental relation between the hydrogen (H)-bonding arrangement of a set of ion-solvating water molecules and the chemical activity of this ensemble. We find that the extent to which the nitrosonium ion (NO+)and water form nitrous acid (HONO) and a hydrated proton cluster in the critical trihydrate depends sensitively on the geometrical arrangement of the water molecules in the network. Theoretical analysis of these data details the role of the water network in promoting charge delocalization.