Explosive desorption of guest molecules embedded in amorphous solid water upon its crystallization is known as the “molecular volcano.” Here, we describe an abrupt ejection of ${\mathrm{NH}}_3$ guest molecules from various molecular host films toward a Ru(0001) substrate upon heating, utilizing both temperature programmed contact potential difference and temperature programmed desorption measurements. ${\mathrm{NH}}_3$ molecules abruptly migrate toward the substrate due to either crystallization or desorption of the host molecules, following an “inverse volcano” process considered a highly probable phenomenon for dipolar guest molecules that strongly interact with the substrate.

• Received 17 August 2022
• Accepted 26 January 2023

DOI:https://doi.org/10.1103/PhysRevLett.130.086203