Phase behavior of propane and n-pentane aerosol particles under conditions relevant to Titan

The phase behavior of propane and n-pentane aerosols was studied under conditions relevant to Titan's atmosphere. Pure propane or n-pentane aerosols and mixed aerosols (mixed with either acetylene, carbon dioxide, or water aerosols) were generated in a bath gas cooling cell. The phase behavior of the aerosols was studied using infrared spectroscopy. Pure propane aerosols remained in a disordered phase during the timescale of the experiment, whereas n-pentane aerosols underwent a phase transition from an initially disordered phase into a crystalline phase. For the homogeneous crystallization of n  -pentane aerosols in a nitrogen bath gas the surface and volume nucleation constants were found to range from 10121012 to 1014cm−2s−1 and from 10111011 to 1013cm−3s−1, respectively. The presence of solid acetylene, carbon dioxide, or water aerosols did not affect the phase behavior of propane aerosols but significantly accelerated the crystallization of n-pentane aerosols with acetylene aerosols acting as the most efficient crystallization nuclei.

► IR spectroscopy reveals the phase behavior of propane and n-pentane aerosol particles under Titan conditions.
► Propane aerosols form stable viscous liquid droplets.
► n-Pentane aerosols quickly crystallize on a timescale of minutes.
► The effect of the presence of heterogeneous ice nuclei is discussed.