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.