Efficiency of Thermionic Emission from C60


We have determined the number of delayed electrons emitted from an ensemble of gas-phase C60, excited at 355 nm with light from an unfocused pulsed Nd:YAG laser. Delayed electrons are detected by single particle counting and integrated over a time interval of 0.1 μs ≤ t ≤ 80 μs. At low laser fluence I, the electron number scales as Ip with p = 6.0 ± 0.4. It approaches saturation at a maximum laser fluence of 100 mJ/cm2, equivalent to a power density of 14 MW/cm2, where delayed electron emission reaches a probability of 2.6 ± 1.1% per multiphoton-excited C60. This experimental value is interpreted as a lower limit to the quantum efficiency for electron emission from C60; it provides an upper limit to the efficiency of competing reactions such as dissociation of C60 into C58 + C2. The dependence of the electron number on the temperature of the fullerene source is in good agreement with the number density of C60 in the molecular beam, as computed from published equilibrium vapor pressures.



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The Journal of Physical Chemistry A


ACS Publications

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