Two-step excitation of Rb atoms on He nanodroplets
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
Published online: 14 January 2011
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 52P1/2 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 52S1/2 emission. The LIF spectrum differs from that of the two-photon one-color direct excitation spectrum 52D 52S1/2, indicating that the system does relax vibrationally during the lifetime of the 52P1/2 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 52P1/2 state can be used as a springboard to reach high-lying 2S and 2D states, and possibly create an artificial super-atom.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2011