Study of H2 confined in the highly ordered pores of MCM-48

We present quasi-elastic neutron scattering measurements of the diffusion of H2 adsorbed in porous MCM-48, a silica glass, with an ordered pore network. Quasi-elastic scattering of hydrogen adsorbed within the pore network was used to monitor the liquid-solid transitions of the absorbed fluid. Unlike other porous media of similar pore size, where supercooling of the liquid-solid transition by 3-4 K was observed, no suppression of the transition was observed for MCM-48. Furthermore, no hysteresis between freezing and melting is observed, as in other porous media. The diffusion constant for the confined liquid has been extracted from the measurements, and the hydrogen adsorbed in the MCM-48 has a slightly higher diffusion constant than bulk liquid H2