Isotope effect on adsorbed quantum phases: Diffusion of H₂ and D₂ in nanoporous carbon

Quasielastic neutron scattering of H₂ and D₂ in the same nanoporous carbon at 10-40 K demonstrates extreme quantum sieving, with D₂ diffusing up to 76 times faster. D₂ also shows liquidlike diffusion while H₂ 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 H₂ and 10-13 K for D ₂. At these temperatures, H₂ and D₂ have identical thermal de Broglie wavelengths that correlate with the dominant pore size.