title: Electron spin pumping of Rb atoms on He nanodroplets via nondestructive optical excitation.
abstract: We measured laser-induced-fluorescence (LIF) and beam-depletion (BD) spectra of rubidium atoms (5S-5P transition) on the surface of superfluid helium nanodroplets (M-He_{N} with M=Rb). It is known that when M is a lighter alkali atom electronic excitation always leads to detachment of the excited atom (M;{*}). The dissociation energy, few tens cm;{-1}, comes either as photon excess energy or from the barrierless formation of a M;{*}-He exciplex. We observe that this picture does not hold when M=Rb and the photon excess energy is small: we are able to excite atoms without detaching them from the droplet, thanks to a barrier preventing formation of the exciplex. This system is ideally suited for optical spin pumping in a He nanodroplet, whose achievement we explicitly demonstrate in a pump-probe magnetic circular dichroism experiment.
authors.affiliation: Institute of Experimental Physics, TU Graz, Petersgasse 16, 8010 Graz, Austria, EU.
authors.forename: Gerald
authors.initials: G
authors.lastname: Auböck
authors.forename: Johann
authors.initials: J
authors.lastname: Nagl
authors.forename: Carlo
authors.initials: C
authors.lastname: Callegari
authors.forename: Wolfgang E
authors.initials: WE
authors.lastname: Ernst