thermal ionization

in mass spectrometry
https://doi.org/10.1351/goldbook.T06303
Takes place when an atom or molecule interacts with a heated surface or is in a gaseous environment at high temperature. Examples of the latter may be a capillary arc plasma, a microwave plasma or an inductively coupled plasma.
Sources:
Orange Book, 2nd ed., p. 203 [Terms]
PAC, 1991, 63, 1541. (Recommendations for nomenclature and symbolism for mass spectroscopy (including an appendix of terms used in vacuum technology). (Recommendations 1991)) on page 1548 [Terms] [Paper]