Isotope Effect on Adsorbed Quantum Phases: Diffusion of H2 and D2 in Nanoporous Carbon

Quasielastic neutron scattering of H-2 and D-2 in the same nanoporous carbon at 10-40 K demonstrates extreme quantum sieving, with D-2 diffusing up to 76 times faster. D-2 also shows liquidlike diffusion while H-2 exhibits Chudley-Elliott jump diffusion, evidence of their different relationships with the local lattice of adsorption sites due to quantum effects on intermolecular interactions. The onset of diffusion occurs at 22-25 K for H-2 and 10-13 K for D-2. At these temperatures, H-2 and D-2 have identical thermal de Broglie wavelengths that correlate with the dominant pore size.