Time-resolved photo-electron spectroscopy on mass-selected metal clusters using a regenerative femtosecond amplifier up to 100 Hz |
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Authors: | N Pontius PS Bechthold M Neeb W Eberhardt |
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Institution: | Forschungszentrum Jülich GmbH, Institut für Festk?rperforschung, 52425 Jülich, Germany, DE
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Abstract: | A femtosecond photo-electron experiment is described which provides excellent conditions for measuring time-resolved photo-electron
spectra of free, monodispersed cluster anions using repetition rates up to 100 Hz. Cluster anions are synthesized in an electric
arc and subsequently cooled in a helium carrier gas. A time-of-flight spectrometer is used for mass separation of the negatively
charged clusters. The kinetic energy of the photo-electrons is analyzed by a magnetic-bottle time-of-flight spectrometer,
which guarantees a maximum collection efficiency. Femtosecond laser pulses are generated by a seeded regenerative Ti:Sa amplifier,
which is externally pumped with the second harmonic of a diode-pumped solid-state Nd:YAG laser. A retroreflector mounted on
a computer-controlled translation stage serves as a reproducible time delay of the probe pulse. The high energy output of
the laser pulses (∼3 mJ) in combination with the variable repetition rate and the high stability of the amplified pulses provide
excellent conditions for recording pump-probe photo-electron spectra of mass-separated cluster anions even at the fairly low
ion density of pulsed plasma cluster sources. First results on the electron dynamics of the Pt3
- cluster demonstrate the reliability of the whole system. Further experimental investigations will concentrate on electron-relaxation
processes in transition- and noble-metal clusters as well as on the nuclear and transition-state dynamics of chemically reacted
adsorbate clusters.
Received: 7 January 2000 / Published online: 7 August 2000 |
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Keywords: | PACS: 33 80 Eh 36 40 -c 42 65 Re |
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