title: Alkali-helium snowball complexes formed on helium nanodroplets.
abstract: We systematically investigate the formation and stability of snowballs formed by femtosecond photoionization of small alkali clusters bound to helium nanodroplets. For all studied alkali species Ak = (Na,K,Rb,Cs) we observe the formation of snowballs Ak(+)He(N) when multiply doping the droplets. Fragmentation of clusters Ak(N) upon ionization appears to enhance snowball formation. In the case of Na and Cs we also detect snowballs Ak(2) (+)He(N) formed around Ak dimer ions. While the snowball progression for Na and K is limited to less than 11 helium atoms, the heavier atoms Rb and Cs feature wide distributions at least up to Ak(+)He(41). Characteristic steps in the mass spectra of Cs-doped helium droplets are found at positions consistent with predictions on the closure of the first shell of helium atoms around the Ak(+) ion based on variational Monte Carlo simulations.
authors: Physikalisches Institut, Universität Freiburg, 79104 Freiburg, Germany.
authors: S
authors: S
authors: Müller
authors: M
authors: M
authors: Mudrich
authors: F
authors: F
authors: Stienkemeier
mesh_terms: D019281:Dimerization; D006371:Helium / Q000737:chemistry*; D013058:Mass Spectrometry; D008672:Metals, Alkali / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry*
chemical_list: D008672:Metals, Alkali; D006371:Helium