Shedding new light on thermionic electron emission of fullerenes

Tunable pulsed infrared (IR) radiation from a free electron laser is used to selectively excite fullerenes via their vibrational modes to very high internal energies. After absorbing several hundred IR photons, the molecules can autoionize. Ion creation is unexpectedly slow, occurring at times beyond 0.1 ms after laser excitation, but is found to be significantly faster for electronically preexcited molecules. It is concluded that reaching the first electronically excited state is a high hurdle on the way from hot molecules to ions.