An approach was proposed for evaluating the average velocities of adsorbate molecules in one-dimensional nanopores, when quantum tunneling between neighboring potential minima led to a non-zero velocity. The approach was used to calculate hydrogen isotope molecule (H2, D2, T2) velocities in ultra-thin carbon single-wall nanotubes, (3,3) and (6,0). It was shown that the isotope mass difference led to large differences in the quantum tunneling value and large differences in the average molecule velocities; especially within the (6,0) tube. It was shown that different tube chiralities led to markedly different velocities of the adsorbate molecules; even if the diameters of the nanotubes did not differ significantly.

Isotope Velocity Differentiation in Thin Carbon Nanotubes through Quantum Diffusion. A.S.Fedorov, P.V.Avramov, S.G.Ovchinnikov, G.Kresse: Europhysics Letters, 2003, 63[2], 254-60