Döppner Tilo, Diederich Thomas, Göde Sebastian, Przystawik Andreas, Tiggesbäumker Josef, Meiwes-Broer Karl-Heinz
Institut für Physik, Universität Rostock, Universitätsplatz 3, 18051 Rostock, Germany.
J Chem Phys. 2007 Jun 28;126(24):244513. doi: 10.1063/1.2745294.
Metal clusters embedded in ultracold helium nanodroplets are exposed to femtosecond laser pulses with intensities of 10(13)-10(14) W/cm2. The influence of the matrix on the ionization and fragmentation dynamics is studied by pump-probe time-of-flight mass spectrometry. Special attention is paid to the generation of helium snowballs around positive metal ions (Me(z+)He(N), z=1,2). Closings of the first and second helium shells are found for silver at N(1)=10,12 and N(2)=32,44, as well as for magnesium at N1=19-20. The distinct abundance enhancement of helium snowballs in the presence of isolated atoms and small clusters in the droplets is used as a diagnostics to explore the cage effect. For silver, a reaggregation of the clusters is observed at 30 ps after femtosecond laser excitation.
