Contribution of restricted rotors to quantum sieving of hydrogen isotopes

The rotational eigenvalues of isotopically substituted hydrogen molecules adsorbed into single-walled carbon nanotubes are calculated using a semiclassical method and using a model potential. The resulting eigenvalues are used to calculate the separation factors due to rotational confinement between different isotopic species as a function of temperature and nanotube size. The results show that even for small shifts in the eigenvalues, significant fractionations should occur, suggesting possible application as an isotope-separation technique.