Mass distribution of ejected molecules and clusters in noncascade sputtering processes

A model of noncascade sputtering is proposed to explain the mass distribution observed by MacFarlane and co-workers in the sputtering of insulin by 90 MeV 127I20+ ions. The ejection of molecular ions from insulin is considered to be induced by vibrational excitation. The ensuing calculations using RRKM theory show that the relative abundance of the ejected species can be fitted to our model yielding realistic values for both the energy deposited by the incident ion and the activation energies required for the ejection of the molecular species.