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

Abstract

Contrary to expectation, droplets did not nucleate in the critical fluid of isobutene. Droplets formed only at $\frac{T}{T_c}<~0.96$, where $\frac{n}{n_c}<~0.38$. In low-density vapor, droplet formation began at a temperature greater than the coexistence temperature at that density. The magnitude of the gap ($T_{\mathrm{onset}}-T_{\mathrm{coexist}}$) correlated with the surface tension of the liquid at $T_{\mathrm{onset}}$. Average droplets in the coexistence vapor contained 730 000 molecules at 297 K and 2000 molecules at 397 K.