By means of grazing incidence x-ray diffraction, the structure of a behenic acid monolayer spread over chloride salt solutions of cadmium is observed to evolve from the tilted $L_2$ phase to the superstructure (corresponding to an organized monolayer of ions in addition to the ordered organic film), through an intermediate phase. The studied salt concentrations are below the so-called “threshold” needed for the formation of this superstructure. This kinetic process involving two first-order phase transitions is confirmed by Brewster angle microscopy experiments and surface pressure-area isotherms measured at different times after monolayer deposition.

• Received 8 March 2004

DOI:https://doi.org/10.1103/PhysRevE.70.050601