Two-step excitation of Rb atoms on He nanodroplets M. Theisen, F. Lackner, F. Ancilotto, C. Callegari and W. E. Ernst Eur. Phys. J. D, 61 2 (2011) 403-408 Published online: 14 January 2011 DOI: 10.1140/epjd/e2010-10504-5