Anomalous nucleation near a fluid phase boundary created by a rapid heat pulse

We report a novel method to rapidly nucleate vapor in a liquid with an electrically pulsed wire that temporarily raises the temperature of nearby liquid. This temperature increase is sufficient to overcome the nucleation barrier to vapor formation by locally putting the system in a non-equilibrium superheated state. By observing the subsequent behavior of bubbles after nucleation and thermal relaxation, we can determine the stability of the vapor phase. We map out a phase envelope by adjustment of the ambient temperature and pressure of the fluid around the wire. We find good agreement between measurements with this method and those made using a conventional apparatus. Surprisingly, we find that rapid heating of the liquid around the wire is able to produce nucleation in certain fluid mixtures for which the temperature increase is not expected to create an unstable or even metastable liquid. Evidence suggests a temporary enrichment of the region around the wire by lighter components due to the Soret effect is responsible for nucleation in such cases.