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Issue 23, 2006
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Investigations of the hygroscopic properties of ammonium sulfate and mixed ammonium sulfate and glutaric acid micro droplets by means of optical levitation and Raman spectroscopy

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Abstract

In the presented work an optical levitation technique performed by means of a focused laser beam, Mie and Raman spectroscopy have been utilized for measuring hygroscopic growth curves and composition of laboratory generated single ammonium sulfate (AS) and internally mixed ammonium sulfateglutaric acid (GA) droplets in the micrometer range. The generated particles have been found to immediately supersaturate (above 45wt% for AS) at 297 K after capturing in the laser beam. Further increase of the relative humidity (RH) up to 85% does not dilute the droplets under the saturation point. A spontaneous hygroscopic growth takes place at 73.5–78% RH for pure AS. The particle grows with an average factor of 1.62 at the deliquescence relative humidity (DRH). Efflorescence of AS occurs at 43% RH with a corresponding concentration of more than 85wt%. Independent of the mixing ratios in ranges 25/75, 50/50, 75/25% AS/GA mixed particles don’t exist as a metastable supersaturated solution droplets in the 35–85% RH range. Instead of growing with increasing relative humidity internally mixed particles build up a solid crystalline layer on the surface. This crystalline phase is not further influenced by ambient relative humidities.

Graphical abstract: Investigations of the hygroscopic properties of ammonium sulfate and mixed ammonium sulfate and glutaric acid micro droplets by means of optical levitation and Raman spectroscopy

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Publication details

The article was received on 27 Mar 2006, accepted on 05 May 2006 and first published on 16 May 2006


Article type: Paper
DOI: 10.1039/B604439E
Citation: Phys. Chem. Chem. Phys., 2006,8, 2759-2764
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    Investigations of the hygroscopic properties of ammonium sulfate and mixed ammonium sulfate and glutaric acid micro droplets by means of optical levitation and Raman spectroscopy

    N. Jordanov and R. Zellner, Phys. Chem. Chem. Phys., 2006, 8, 2759
    DOI: 10.1039/B604439E

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