One- and two-photon spectroscopy of highly excited states of alkali-metal atoms on helium nanodroplets

Alkali-metal atoms captured on the surface of superfluid helium droplets are excited to high energies (approximate to 3 eV) by means of pulsed lasers, and their laser-induced-fluorescence spectra are recorded. We report on the one-photon excitation of the (n+1) p <- ns transition of K, Rb, and Cs (n=4, 5, and 6, respectively) and on the two-photon one-color excitation of the 5d <- 5s transition of Rb. Gated-photon-counting measurements are consistent with the relaxation rates of the bare atoms, hence consistent with the reasonable expectation that atoms quickly desorb from the droplet and droplet-induced relaxation need not be invoked. (C) 2010 American Institute of Physics.