The Molecular Volcano: Abrupt CCl4Desorption Driven by the Crystallization of Amorphous Solid Water

The desorption kinetics of molecular beam deposited ultrathin films of CC${\mathrm{l}}_4$ and amorphous solid water (ASW) are studied. Overlayers of ASW impede CC${\mathrm{l}}_4$ desorption until the onset of crystallization, whereupon the CC${\mathrm{l}}_4$ desorbs abruptly. The abrupt desorption occurs through connected pathways that are formed in the water overlayer during the nucleation and growth of crystalline ice from ASW. The onset of the abrupt desorption corresponds to the threshold for dynamic percolation. As the crystallization proceeds, the number of connected pathways rapidly increases, giving rise to the episodic release of CC${\mathrm{l}}_4$.