a) What is the difference between ionization energy (IE) and appearance energy (AE)?
The ionization energy (IE) is defined as the minimum amount of energy which has to be absorbed by an atom or molecule in its electronic and vibrational ground states form an ion that is also in its ground states by ejection of an electron.
The amount of energy needed to be transferred to the neutral M to allow for the detection of a certain fragment ion is called appearance energy (AE) of that fragment ion.
b) What is the meaning of kinetic shift?
The kinetic shift denotes the overestimation of AEs due to the contribution of excess energy in the transition state necessary to yield rate constants larger than 106 s–1.
c) How does kinetic shift affect IE and AE measurements?
The effect of kinetic shift only applies to AE measurements because the effectively measured AE is influenced by the rate of the respective fragmentation process.
In contrast to AEs, there are no kinetics in electron ionization or photoionization and thus no kinetic shift on IEs is observed.