Eur. Phys. J. D 61, 403-408 (2011)
https://doi.org/10.1140/epjd/e2010-10504-5

Two-step excitation of Rb atoms on He nanodroplets

¹ Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria
² Dipartimento di Fisica `G. Galilei', Università di Padova, via Marzolo 8, 35131 Padova, Italy
³ CNR-IOM-Democritos, 34014 Trieste, Italy

Corresponding authors: ^a moritz.theisen@tugraz.at - ^b wolfgang.ernst@tugraz.at

Received: 13 September 2010
Published online: 14 January 2011

Abstract

We present the first sequential laser excitation of atom-doped helium nanodroplets. Rubidium atoms on the surface of helium nanodroplets are selectively excited with a continuous wave laser to the 5²P_1/2 state so as not to desorb from the nanodroplets. From there they are excited by a laser pulse to the 5²D state; a laser-induced fluorescence (LIF) spectrum is recorded by monitoring the 6²P 5²S_1/2 emission. The LIF spectrum differs from that of the two-photon one-color direct excitation spectrum 5²D 5²S_1/2, indicating that the system does relax vibrationally during the lifetime of the 5²P_1/2 state. To model the LIF spectra we use calculated energy levels of the Rb atom as a function of its distance R from the center of the helium nanodroplet. The Franck-Condon factors of the resulting potential energy curves agree with the experimental spectra. In the future the 5²P_1/2 state can be used as a springboard to reach high-lying ²S and ²D states, and possibly create an artificial super-atom.