@article {1516,
	title = {Crystallization of aqueous ammonium sulfate particles internally mixed with soot and kaolinite: Crystallization relative humidities and nucleation rates},
	journal = {Journal of Physical Chemistry A},
	volume = {110},
	number = {28},
	year = {2006},
	note = {ISI Document Delivery No.: 063EXTimes Cited: 12Cited Reference Count: 70Pant, Atul Parsons, Matthew T. Bertram, Allan K.},
	month = {Jul},
	pages = {8701-8709},
	type = {Article},
	abstract = {Using optical microscopy, we investigated the crystallization of aqueous ammonium sulfate droplets containing soot and kaolinite, as well as the crystallization of aqueous ammonium sulfate droplets free of solid material. Our results show that soot did not influence the crystallization RH of aqueous ammonium sulfate particles under our experimental conditions. In contrast, kaolinite increased the crystallization RH of the aqueous ammonium sulfate droplets by approximately 10\%. In addition, our results show that the crystallization RH of aqueous ammonium sulfate droplets free of solid material does not depend strongly on particle size. This is consistent with conclusions made previously in the literature, based on comparisons of results from different laboratories. From the crystallization results we determined the homogeneous nucleation rates of crystalline ammonium sulfate in aqueous ammonium sulfate droplets and the heterogeneous nucleation rates of crystalline ammonium sulfate in aqueous ammonium sulfate particles containing kaolinite. Using classical nucleation theory and our experimental data, we determined that the interfacial tension between an ammonium sulfate critical nucleus and an aqueous ammonium sulfate solution is 0.064 +/- 0.003 J m(-2) (in agreement with our previous measurements), and the contact angle between an ammonium sulfate critical nucleus and a kaolinite surface is 59 +/- 2. On the basis of our results, we argue that soot will not influence the crystallization RH of aqueous ammonium sulfate droplets in the atmosphere, but kaolinite can significantly modify the crystallization RH of atmospheric ammonium sulfate droplets. As an example, the CRH50 ( the relative humidity at which 50\% of the droplets crystallize) ranges from about 41 to 51\% RH when the diameter of the kaolinite inclusion ranges from 0.1 to 5 mu m. For comparison, the CRH50 of aqueous ammonium sulfate droplets (0.5 Am diameter) free of solid material is approximately 34.3\% RH under atmospheric conditions.},
	keywords = {AEROSOL-PARTICLES, ATMOSPHERIC AEROSOL, deliquescence, HETEROGENEOUS NUCLEATION, HYGROSCOPIC GROWTH, MINERAL DUST, ORGANIC-COMPOUNDS, PHASE-TRANSITIONS, TROPOSPHERIC AEROSOLS, WATER-UPTAKE},
	isbn = {1089-5639},
	url = {<Go to ISI>://000239001600013},
	author = {Pant, A. and Parsons, M. T. and Bertram, A. K.}
}
@article {1519,
	title = {Crystallization of aqueous inorganic-malonic acid particles: Nucleation rates, dependence on size, and dependence on the ammonium-to-sulfate},
	journal = {Journal of Physical Chemistry A},
	volume = {110},
	number = {26},
	year = {2006},
	note = {ISI Document Delivery No.: 058DRTimes Cited: 16Cited Reference Count: 63},
	month = {Jul},
	pages = {8108-8115},
	type = {Article},
	abstract = {Using an electrodynamic balance, we determined the relative humidity ( RH) at which aqueous inorganic-malonic acid particles crystallized, with ammonium sulfate ((NH4)(2)SO4), letovicite ((NH4)(3)H(SO4)(2)), or ammonium bisulfate (NH4HSO4) as the inorganic component. The results for (NH4)(2)SO4-malonic acid particles and (NH4)(3)H(SO4)(2)-malonic acid particles show that malonic acid decreases the crystallization RH of the inorganic particles by less than 7\% RH when the dry malonic acid mole fraction is less than 0.25. At a dry malonic acid mole fraction of about 0.5, the presence of malonic acid can decrease the crystallization RH of the inorganic particles by up to 35\% RH. For the NH4HSO4-malonic acid particles, the presence of malonic acid does not significantly modify the crystallization RH of the inorganic particles for the entire range of dry malonic acid mole fractions studied; in all cases, either the particles did not crystallize or the crystallization RH was close to 0\% RH. Size dependent measurements show that the crystallization RH of aqueous (NH4)(2)SO4 particles is not a strong function of particle volume. However, for aqueous (NH4)(2)SO4-malonic acid particles ( with dry malonic acid mole fraction) 0.36), the crystallization RH is a stronger function of particle volume, with the crystallization RH decreasing by 6 +/- 3\% RH when the particle volume decreases by an order of magnitude. To our knowledge, these are the first size dependent measurements of the crystallization RH of atmospherically relevant inorganic-organic particles. These results suggest that for certain organic mole fractions the particle size and observation time need to be considered when extrapolating laboratory crystallization results to atmospheric scenarios. For aqueous (NH4)(2)SO4 particles, the homogeneous nucleation rate data are a strong function of RH, but for aqueous (NH4)(2)SO4-malonic acid particles (with dry organic mole fraction = 0.36), the rates are not as dependent on RH. The homogeneous nucleation rates for aqueous (NH4)(2)SO4 particles were parametrized using classical nucleation theory, and from this analysis we determined that the interfacial surface tension between the crystalline ammonium sulfate critical nucleus and an aqueous ammonium sulfate solution is between 0.053 and 0.070 J m(-2).},
	keywords = {AEROSOL-PARTICLES, ATMOSPHERIC PARTICLES, BALANCE, ELECTRODYNAMIC, HETEROGENEOUS NUCLEATION, HYGROSCOPIC PROPERTIES, MIXTURES, ORGANIC-COMPOUNDS, PHASE-TRANSITIONS, RELATIVE-HUMIDITY, WATER-UPTAKE},
	isbn = {1089-5639},
	url = {<Go to ISI>://000238645600017},
	author = {Parsons, M. T. and Riffell, J. L. and Bertram, A. K.}
}
