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Author Oberreit, Derek ♦ Rawat, Vivek K. ♦ Larriba-Andaluz, Carlos ♦ Ouyang, Hui ♦ McMurry, Peter H. ♦ Hogan, Christopher J.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY ♦ ADSORPTION ♦ CESIUM ♦ CESIUM IODIDES ♦ COLLISIONS ♦ COMPARATIVE EVALUATIONS ♦ CROSS SECTIONS ♦ ION PAIRS ♦ IONS ♦ MASS SPECTROMETERS ♦ MASS SPECTROSCOPY ♦ MOLECULES ♦ POTASSIUM IODIDES ♦ RUBIDIUM ♦ SODIUM IODIDES ♦ UPTAKE ♦ WATER ♦ WATER VAPOR
Abstract The sorption of vapor molecules onto pre-existing nanometer sized clusters is of importance in understanding particle formation and growth in gas phase environments and devising gas phase separation schemes. Here, we apply a differential mobility analyzer-mass spectrometer based approach to observe directly the sorption of vapor molecules onto iodide cluster ions of the form (MI){sub x}M{sup +} (x = 1-13, M = Na, K, Rb, or Cs) in air at 300 K and with water saturation ratios in the 0.01-0.64 range. The extent of vapor sorption is quantified in measurements by the shift in collision cross section (CCS) for each ion. We find that CCS measurements are sensitive enough to detect the transient binding of several vapor molecules to clusters, which shift CCSs by only several percent. At the same time, for the highest saturation ratios examined, we observed CCS shifts of up to 45%. For x < 4, cesium, rubidium, and potassium iodide cluster ions are found to uptake water to a similar extent, while sodium iodide clusters uptake less water. For x ≥ 4, sodium iodide cluster ions uptake proportionally more water vapor than rubidium and potassium iodide cluster ions, while cesium iodide ions exhibit less uptake. Measured CCS shifts are compared to predictions based upon a Kelvin-Thomson-Raoult (KTR) model as well as a Langmuir adsorption model. We find that the Langmuir adsorption model can be fit well to measurements. Meanwhile, KTR predictions deviate from measurements, which suggests that the earliest stages of vapor uptake by nanometer scale species are not well described by the KTR model.
ISSN 00219606
Educational Use Research
Learning Resource Type Article
Publisher Date 2015-09-14
Publisher Place United States
Journal Journal of Chemical Physics
Volume Number 143
Issue Number 10


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