Collisional formation and dissociation of Na@C60+

The dissociation rate constant of a microcanonical ensemble of endohedral Na@C60+, formed by gas-phase collisions, is determined to be 94 000 s−1 when the internal excitation energy reaches 49.1±0.5 eV. A model that includes radiative cooling and a distribution of energies, accurately reproduces the yield of Na@C60+ from its appearance at 29.6 eV to its disappearance above 55 eV. Assuming an Arrhenius factor of ν0=5×1019 s−1 we derive a dissociation energy of 10.17±0.02 eV (statistical error). The abruptness of the breakdown graph implies a lower limit for ν0.