Research Group: Heterogeneous Chemistry Project

Members

Scientific Objectives

We are interested in, and perform laboratory studies pertaining to, the general areas of: the Heterogeneous Chemistry of the atmosphere, the Nucleation of particles in the atmosphere, and the application of Chemical Ionization Mass Spectrometry (Proton Transfer Mass Spectrometry) to these types of problems. Representative examples of ongoing research within our laboratory are sketched below.

Heterogeneous Chemistry

Uptake of Strong Acids and Bases by Dilute Sulfuric Acid Solutions: Studies of Mass Accommodation

Gas Phase Monitoring by CIMS uptake onto dispersed aerosol particles of
NH3, H2SO4, CH3SO3H Np = 104-105 cm-3, ln-normal distribution: rp = 50-100 nm, lns = ~0.3

Results

  • aNH3 = 1.0(+/-0.15), Hanson and Kosciuch, J. Phys. Chem., 2003.
  • aH-X = 0.86 (+/-0.17)for H2SO4 and CH3SO3H, manuscript in preparation

Significance

  • Determines aerosol particle growth rates = efficient!
  • Accommodation likely does not impede heterogenous rxns

Uptake of Organic species by aqueous liquids

  • Nopinone solubility in water, Noziere et al., Geophys. Res. Lett., 2002. H ~ 100 M / atm.
  • Solubility and reactions of Methyl Vinyl Ketone, Methacrolein, 2-methyl,3-buten-2-ol (MBO) in 20-80 wt.% H2SO4 solutions and water, manuscript in preparation

Nucleation

Particle formation in dilute mixtures of H2SO4 (and NH3) in humidified N2

Gas Phase Monitoring by CIMS particle sizes, detected by
NH3, H2SO4 ~2-to-10 nm diameter, UFACNC, sizing with pulse height analysis-UFACNC and nano-DMA

Results:

  • at RH < 20%, ,J(number of particles cm-3 s-1) = Cx[H2SO4]8[H2O]5, Ball et al., J. Geophys. Res., 1999.
  • For NH3 levels estimated at 1-to-10 pptv (0.8 atm total pressure), J was enhanced by an order of magnitude.

Significance

  • Definitive effect of ammonia on nucleation rates
  • Decent agreement with previous measurements of J dependence upon RH and acidity.

Molecular clusters

  • Detection of molecular clusters, (H2SO4)n (H2O)m at levels up to 107 cm-3, for n = 2-to-8, ~ 250 K.
  • ..with NH3 at ~ 100 pptv, (H2SO4)n (NH3)m(H2O)o at levels up to 107 cm-3, for n = 2-to-8, m = 0-to-(n-1), 250-to-280 K.

PTrMS development

  • Ion drift region at p = 10 torr. Instrument description and evaluation in a sensitivity study (methanol, acetaldehyde, acetone, isoprene, alpha-pinene) Hanson et al., IJMS, 223-224, 2003, 507-518.
  • Application to laboratory studies of the oxidation of methane, ethane, cyclohexane, cyclopentane. Ion-molecule rate coefficients of selected peroxyls with H3O+(H2O)n. Hanson et al., IJMS, 22_, 2004,