Pressure-Driven Dissociation of a Kr Clathrate in the Presence of Colloids

Clathrate hydrates (CH) are nonstoichiometric water structures stabilized by hydrophobic molecules, usually at high pressures or low temperatures. Once formed at a certain temperature, their ice-like structures are stable unless the pressure is reduced below critical dissociation values. We explore CH of noble gases using coherence-gated light to perform Fresnel reflectometry (FR) and dynamic light scattering (DLS) in an optically isolated picoliter-sized volume located at the tip of an optical fiber. FR allows us to observe the change in the effective refractive index (n_eff), providing a clear indication of the formation of CH and its porous properties. We found that krypton (Kr) forms CH with higher porosity compared to xenon (Xe), with porosities around 0.54 and 0.02, respectively. Furthermore, by performing DLS measurements, we discovered that in the presence of micrometer-sized particles, Kr CH dissociate with increasing gas pressure. This unexpected phenomenon is due to the Brownian dynamics produced by the Kr atoms accumulated in the highly porous material.