Isotope velocity differentiation in thin carbon nanotubes through quantum diffusion

An approach is proposed to evaluate the average velocities of adsorbate molecules in one-dimensional nanopore, when quantum tunneling between neighboring potential minima leads to nonzero velocity. The approach is used to calculate the hydrogen isotope molecule (H₂, D₂, T₂) velocities in ultrathin carbon single-wall nanotubes (SWNT) (3,3) and (6,0). It is shown that the isotope mass difference leads to large differences of the quantum tunneling value and large differences of the average molecule velocities, especially inside the tube (6,0). It is shown that different tube chirality leads to drastically different velocities of adsorbate molecules, even if the diameters of both nanotubes do not differ significantly.