thermal ionization

in mass spectrometry
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.
Source:
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
Orange Book, p. 203