Pump-probe measurements of C60

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Pump-probe measurements of C60

• Hannover, Germany March 2003

M. Boyle, K. Hoffmann, C.P.Schulz I.V. Hertel
Eleanor Campbell, Göteborg University Chalmers,
Sweden
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Experimental Introduction
JCP 112 (2000) 2781
Photo-electron and Photo-ion spectroscopy to
study C60
Energy Redistribution Excitation and ionization
mechanisms
Recent interest lies in the 4-photon with 800nm
(or 2-photon with 400nm) transition, where
Rydberg Series have been observed
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Photoelectron Spectra of C60
BEhn-KE
Boyle, et al. PRL 87 (2001)273401
assuming 1 photon
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Bandwidth Limited Pulse Duration DEDt0.441
DEmeas DElaser ? DEdecay DElaser DEradiative
decay ltlt DElaser Lifetimes of Rydberg states
are 400 fs or longer
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Two Color Measurements

• Defocused 400nm beam (to equalize focal lengths)
• Orientation of polarization so that directly
  excited electrons from
• different colors independently measured
• Scanned red pulse in time

Polarization Orientation
Time Orientation
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Two Color Pump-Probe Electrons
Rydberg Peaks
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Time Decay of Rydberg Series
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Decay Time of Rydberg Series
Increasing KE ? higher Rydberg level ? longer
lifetime ? slower decay
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Two Color Experimental Summary
Measurement was sensitive to 800nm electrons and
not 400 nm electrons (due to polarization
orientation)
Apparent decay of Rydberg levels on few hundred
femtosecond time scale
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Next Experimental Steps
1.) Different Wavelengths (avoid lower
resonance) 2.) PEPICO - to correlate electron
to ion 3.) angular distribution of electrons