The energetics and dynamics of unimolecular decompositions of C-70(+) and its noble gas endohedral cations, Ne@C-70(+) and Ar@C-70(+), have been studied using tandem mass spectrometry techniques. The high-resolution mass-analyzed ion kinetic energy (HR-MIKE) spectra for the unimolecular reactions Of C-70(+), Ne@C-70(+), and Ar@C-70(+) were recorded by scanning the electrostatic analyzer and using single-ion counting that was achieved by combination of an electron multiplier, amplifier/discriminator, and multichannel analyzer. These cations dissociate unimolecularly via loss of a C-2 unit, and no endohedral atom is observed as fragment. The activation energies for C-2 evaporation from Ne@C-70(+) and Ar@C-70(+) are lower than those for elimination of the endohedral noble gas atoms. The kinetic energy release distributions (KERDs) for the C-2 evaporation have been measured and, by use of the finite heat bath theory (FHBT), the binding energies for the C-2 emission have been deduced from the KERDs. The C-2 evaporation energies increase in the order Delta E-vap(C-70(+)) < Delta E-vap(Ne@C-70(+)) < Delta E-vap(Ar@C-70(+)), but no big difference in the cage binding was observed for C-70(+), Ne@C-70(+), and Ar@C-70(+), indicating incorporations of the Ne and Ar atoms into C-70 Contribute a little to the stability Of C-70 toward C, loss, which is in good agreement with theoretical calculations but contrasts with the findings in their C-60 analogues and in metallofullerenes that the decay energies of the filled fullerenes are much higher than those of the corresponding empty cages.