This article reviews, on the basis of mass spectrometric experiments, the c
urrent status concerning the C-2 binding energy or evaporation energy in C-
60, D(C-58-C-2)= Delta E-vap(C-60). Kinetic energy release distributions, t
ime-resolved metastable fractions, breakdown curves, and thermionic emissio
n rates all point to Delta E-vap(C-60(+)) greater than or equal to 9.5 eV a
nd Delta E-vap(C-60) greater than or equal to 10 eV. These results are in a
greement with high-level ab initio density functional theory calculations a
nd with expectations from the known heats of formation of C-60, C-70, and C
-2. The C-2 evaporation is characterized by a very loose transition state w
ith a pre-exponential factor close to the calculated upper limit. (C) 2000
Elsevier Science B.V.