Droplet Nucleation by Gas-Phase Positive Ions, Observed through Mobility

Contrary to expectation, droplets did not nucleate in the critical fluid of isobutene. Droplets formed only at TTc<~0.96, where nnc<~0.38. In low-density vapor, droplet formation began at a temperature greater than the coexistence temperature at that density. The magnitude of the gap (Tₒₙₛₑₜ-Tcoexist) correlated with the surface tension of the liquid at Tₒₙₛₑₜ. Average droplets in the coexistence vapor contained 730 000 molecules at 297 K and 2000 molecules at 397 K.