| Abstract: | NH3/C2H2 aerosols were formed in a bath gas cooling cell at cryogenic temperatures and studied using infrared spectroscopy. The infrared band shapes associated with these particles were quite different from those of the pure solids and vibrational shifts of up to 100 wavenumbers were observed. The phase of these particles was identified as a NH3?·?C2H2 co-crystal and was found to be thermodynamically stable with respect to the solids of pure NH3 and C2H2. Experiments with core–shell structures demonstrated that the co-crystalline phase could also be formed through a solid state reaction of pure NH3 and C2H2 in aerosol particles. The results of this work are relevant to planetary atmospheres where both NH3 and C2H2 are present, as the co-crystalline phase can readily form in mixed particles of these substances and its optical properties cannot be understood by simply considering the pure substances. |
