Ionization and plasma formation in high n cold Rydberg samples W. Li, P. J. Tanner, Y. Jamil and T. F. Gallagher Eur. Phys. J. D, 40 1 (2006) 27-35 Published online: 18 August 2006 DOI: 10.1140/epjd/e2006-00189-8