desublimering

Desublimering, or desublimation, is the phase transition in which a substance changes directly from a gas to a solid, bypassing the liquid phase. It is the reverse process of sublimation. Desublimation occurs under conditions where a vapor is cooled or pressurized to lie on or below the solid’s stability line, making solid deposition more stable than a liquid phase.

In thermodynamic terms, deposition releases latent heat and proceeds via nucleation, often aided by a surface or impurities that provide a template for crystal formation. The process is favored when the ambient temperature is well below the substance’s sublimation point and the vapor pressure of the solid is favorable relative to the surrounding gas.

Natural phenomena commonly involve desublimation. In the atmosphere, water vapor can desublimate as ice, forming hoar frost and frost crystals on cold surfaces such as windows, vegetation, or exposed ground. Deposition of water vapor into ice also contributes to specific frost patterns and to cloud ice formation in high-altitude or polar environments.

In industrial and scientific contexts, desublimation is used in vapor-deposition techniques to grow crystalline solids or thin films from vapors, often under controlled temperatures and pressures. Cold-trap systems and certain cryogenic applications rely on deposition of vapors onto cold surfaces to remove gases from a chamber.

See also: sublimation, condensation, deposition.