Gravity-induced diffusion of isotope atoms in monoatomic solid Se T. Mashimo, M. Ono, X. S. Huang, Y. Iguchi, S. Okayasu, K. Kobayashi and E. Nakamura EPL, 81 5 (2008) 56002 Published online: 19 February 2008 DOI: 10.1209/0295-5075/81/56002