Ice nucleation rates near ∼225 K

Area of Science:

• Physical Chemistry
• Atmospheric Science
• Materials Science

Background:

• Understanding ice nucleation in atmospheric aerosols is crucial for climate modeling.
• Previous studies on homogeneous and heterogeneous ice nucleation have provided valuable insights.
• The behavior of ice nucleation in nanoscale water droplets remains an active area of research.

Purpose of the Study:

• To measure ice nucleation rates in supercooled nano-droplets.
• To investigate the influence of droplet size and temperature on ice nucleation.
• To compare experimental results with existing nucleation theories.

Main Methods:

• Experiments were conducted on supercooled nano-droplets with radii from 6.6 nm to 10 nm.
• Droplet temperatures were varied from 225 K to 204 K.
• Ice nucleation rates (Jice) were measured and analyzed.

Main Results:

• Ice nucleation rates systematically increased from ~10^21 cm^-3 s^-1 to ~10^22 cm^-3 s^-1 with decreasing temperature.
• Measured rates overlap with previously reported data for similar conditions.
• A sharp change in nucleation rate with temperature was observed, which is difficult to reconcile with current theories.

Conclusions:

• The study provides new experimental data on ice nucleation in nanodroplets.
• Observed rates suggest a smooth extrapolation to larger droplet sizes.
• Current nucleation theories struggle to explain the sharp temperature dependence in nanodroplets due to high internal pressure.