Formation and Dissociation of Dimethyl Ether Clathrate Hydrate in Interstellar Ice Mimics

Clathrate hydrates (CHs) are believed to exist within interstellar environments, potentially contributing to the preservation of diverse volatile compounds within icy bodies across the cosmos. In this study, using reflection absorption infrared spectroscopy, we show the formation of dimethyl ether (DME) CH from a vapor-deposited DME-water amorphous ice mixture. Experiments were conducted in an environment mimicking interstellar conditions: ultrahigh vacuum (P similar to 5 x 10(-10) mbar) and cryogenic conditions (T similar to 10-150 K). Thermal annealing of the amorphous ice mixture to a higher temperature (T similar to 125 K) resulted in the formation of CH. Quantum chemical calculations suggested the formation of 5(12)6(4) cages of structure II CH. Subsequent investigations into the dissociation of DME CH unveiled its transformation into hexagonal ice, requiring a substantial activation energy of 68.04 kJ mol(-1). Additionally, confirmation of the formation and dissociation of CH was supported by temperature-programmed desorption mass spectrometry. These results significantly advance our understanding of the existence of CHs under extreme conditions relevant to an interstellar medium.