The transition from direct to delayed ionisation of C 60

Abstract

The timescale for the coupling of electronic and vibrational excitation in isolated fullerenes is determined by recording positive ion time-of-flight mass spectra on excitation with ultrashort laser pulses at 790 nm of the same fluence but different pulse durations. The coupling leads to the onset of a delayed ionisation "tail" on the parent fullerene ion peak. This occurs for a pulse duration of 500-1000 fs, depending on laser fluence.

Ultrafast excitation, ionization, and fragmentation of C60

“…The fraction of delayed C 60 ions increases almost linearly with the pulse duration. No saturation has been found for pulses up to 5 ps, the longest pulse length available in these experiments (Campbell et al, 2001a). Further insight into mechanisms and time scales of the various energy transfer processes is gleaned from comparing mass spectra at different pulse duration but constant laser intensity (i.e.…”

Excitation of Rydberg Series inC60

“…For intermediate pulse durations the ionization is predominantly statistical from a hot electron bath. Finally, for pulse durations beyond approximately 500 fs [13] the electronic excitation is coupled to vibrational excitation, and the well-known statistical microsecond delayed ionization [1], akin to thermionic emission, is observed. This ps time scale again yields a thermal electron distribution but at a lower temperature than the intermediate ionization process for the same excitation fluence [1].…”

The use of a photoinduced electron-transfer reaction for optical limiting in fullerene-containing solutions

“…The absorption spectra of fullerene radical ions are diverse [8,9]. Our interest is with the applicability of the ë 60 fullerene radical anion to optical limiting.…”