Experimental observation of reduced electronic stopping in photo-excited C-60

Electronic stopping experienced by a keV He+ ion interacting with the valence electrons of a single fullerene is the predominant channel for energy deposition in such collisions. Electronic excitation of the fullerene valence electrons, achieved by absorption of several 532 nm photons, is expected to influence the electronic friction. We use time-of-flight mass spectrometry to investigate the multifragmentation pattern arising from ion-fullerene collisions. This pattern can be considered as an observable for electronic stopping. Comparing results obtained with and without laser excitation, we observe striking changes in multifragmentation which imply that electronic stopping is substantially lower in the photoexcited system.