Berlin 2001 – wissenschaftliches Programm

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A: Atomphysik

A 1: Posters Monday (Cluster, Atoms in Fields)

A 1.5: Poster

Montag, 2. April 2001, 12:30–15:00, AT3

Time-Resolved Spectroscopy of Alkali Halide Cluster — •F. Budzyn, C. Lupulescu, M. Krenz, S. Vajda, and L. Wöste — Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin

The Na_nF_n−1 are systems for investigating the ultrafast nuclear dynamics. They are characterized by a metal bond and one-excess electron, localized either in the halide vacancy or on the alkali atom attached to the ionic subunit [1].The Na clusters are produced in a supersonic jet of Na metal with Ar and SF₆ as carrier gasses at a 70 µm nozzle.The beam was irradiated by ultrashort laser pulses and analyzed by a mass spectrometer. The laser system consists from a Ti:Sa oscillator ,pumped by a Spectra Physics Millennia ,providing seed pulses for a 1 kHz multipass amplifier.The output 50 fs pulses centered at 800 nm are pumping a travelling wave optical parametric amplifier which provides short fm pulses in the region between 250 nm - 2 µm. The photodissociation of the clusters was studied by recording a set of mass spectra at different wavelengths in the region between 512 and 600 nm.The clusters are excited with the first laser pulse (pump). The temporal evolution of the excited state is monitored with a second laser pulse (probe), which ionizes the excited particles after a variable time delay Δt.The transient ion signal reflects the dynamics of the excited state.In the case of Na₂F the first excited state is reached by a laser pulse centered at 1.21 µm, while the probe energy is about 3.1 eV (400 nm).

[1] M.Hartmann,J.Pittner,V.Bonacic-Koutecky, J. Chem. Phys. in press