Appearance energy

Appearance energy (also known as appearance potential) is the minimum energy that must be supplied to a gas phase atom or molecule in order to produce an ion. In mass spectrometry, it is accounted as the voltage to correspond for electron ionization. ^[1] This is the minimum electron energy that produces an ion.^[2] In photoionization, it is the minimum photon energy of a photon that produces some ion signal. For example, the indene bromide ion (IndBr+) only loses bromine at an incident photon energy of 10.2 eV, so the product, indenyl, has an appearance energy of 10.2 eV.^[3]

See also

• Ionization energy