Chemi-ionization

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Not to be confused with chemical ionization.

Chemi-ionization is the formation of an ion through the reaction of a gas phase atom or molecule with another atom or molecule when the collision energy is below the energy required to ionize the reagents.[1][2] The reaction may involve a reagent in an excited state[3] or may result in the formation of a new chemical bond.[1][4] Chemi-ionization can proceed through the Penning, associative, dissociative or rearrangement ionization reactions. Includes reactions that produce a free electron or a pair of ions (positive and negative).[5]

This process is helpful in mass spectrometry because it creates unique bands that can be used to identify molecules.[6] This process is extremely common in nature as it is considered the primary initial reaction in flames.[citation needed]

Terminology[edit]

According to the IUPAC, in the context of mass-spectrography, the term can be defined as "ionization of an atom or molecule by interaction with another internally excited atom or molecule".[3]

History[edit]

The term chemi-ionization was coined by Hartwell F. Calcote in 1948 in the Third Symposium on Combustion and Flame, and Explosion Phenomena.[7] The Symposium performed much of the early investigation into this phenomenon in the 1950s. The majority of the research on this topic was performed in the 1960s and '70s. It is currently seen in many different ionization techniques used for mass spectrometry.[8][9]

Reactions[edit]

Reactions involving a reagent in an excited state[edit]

Chemi-ionization can be represented by

where G is the excited state species (indicated by the super-scripted asterisk), and M is the species that is ionized by the loss of an electron to form the radical cation (indicated by the super-scripted "plus-dot").

Astrophysical implications[edit]

Chemi-ionization has been postulated to occur in the hydrogen rich atmospheres surrounding stars. This type of reaction would lead to many more excited hydrogen atoms than some models account for. This affects our ability to determine the proper optical qualities of solar atmospheres with modeling.[10]

In flames[edit]

The most common example of chemi-ionization occurs in hydrocarbon flame. The reaction can be represented as

[11]

This reaction is present in any hydrocarbon flame and can account for deviation in the amount of expected ions from thermodynamic equilibrium.[12]

See also[edit]

References[edit]

  1. ^ a b Jozef Paulovic; Laura Gagliardi; John M Dyke; Kimihiko Hirao (1 April 2005). "A theoretical study of the gas-phase chemi-ionization reaction between uranium and oxygen atoms". The Journal of Chemical Physics. 122 (14): 144317. doi:10.1063/1.1879832. ISSN 0021-9606. PMID 15847532. Wikidata Q51494633.
  2. ^ Andre Venter; Marcela Nefliu; R. Graham Cooks (April 2008). "Ambient desorption ionization mass spectrometry". Trends in Analytical Chemistry. 27 (4): 284–290. doi:10.1016/J.TRAC.2008.01.010. ISSN 0165-9936. Wikidata Q29541795.
  3. ^ a b Kermit K. Murray; Robert K. Boyd; Marcos N. Eberlin; G. John Langley; Liang Li; Yasuhide Naito (6 June 2013). "Definitions of terms relating to mass spectrometry (IUPAC Recommendations 2013)". Pure and Applied Chemistry. 85 (7): 1515–1609. doi:10.1351/PAC-REC-06-04-06. ISSN 0033-4545. Wikidata Q55872037.
  4. ^ Klucharev, A. N. (1993), "Chemi-ionization processes", Physics-Uspekhi, 36 (6): 486, Bibcode:1993PhyU...36..486K, doi:10.1070/PU1993v036n06ABEH002162
  5. ^ P. Pradel; J. J. Laucagne (1983). "Chemi-ionization reactions involving metastable helium atoms at high energy". Journal de physique. 44 (11): 1263–1271. doi:10.1051/JPHYS:0198300440110126300. ISSN 0302-0738. Wikidata Q125499439.
  6. ^ Dyke, John M.; Shaw, Andrew M.; Wright, Timothy G. (1994). "Study of Chemiionization Reactions in the O + 2-Butyne Reaction Mixture". The Journal of Physical Chemistry. 98 (25): 6327–6331. doi:10.1021/j100076a016. ISSN 0022-3654.
  7. ^ Calcote, Hartwell F. (1948). "Electrical properties of flames". Symposium on Combustion and Flame, and Explosion Phenomena. 3 (1): 245–253. doi:10.1016/S1062-2896(49)80033-X. hdl:2027/uva.x030313059. ISSN 1062-2896.
  8. ^ Chen, Lee Chuin; Yu, Zhan; Hiraoka, Kenzo (2010). "Vapor phase detection of hydrogen peroxide with ambient sampling chemi/chemical ionization mass spectrometry". Analytical Methods. 2 (7): 897. doi:10.1039/c0ay00170h. ISSN 1759-9660.
  9. ^ Mason, Rod S.; Williams, Dylan R.; Mortimer, Ifor P.; Mitchell, David J.; Newman, Karla (2004). "Ion formation at the boundary between a fast flow glow discharge ion source and a quadrupole mass spectrometer". Journal of Analytical Atomic Spectrometry. 19 (9): 1177. doi:10.1039/b400563p. ISSN 0267-9477.
  10. ^ Mihajlov, Anatolij A.; Ignjatović, Ljubinko M.; Srećković, Vladimir A.; Dimitrijević, Milan S. (2011). "CHEMI-IONIZATION IN SOLAR PHOTOSPHERE: INFLUENCE ON THE HYDROGEN ATOM EXCITED STATES POPULATION". The Astrophysical Journal Supplement Series. 193 (1): 2. arXiv:1105.2134. Bibcode:2011ApJS..193....2M. doi:10.1088/0067-0049/193/1/2. ISSN 0067-0049.
  11. ^ Vinckier, C.; Gardner, Michael P.; Bayes, Kyle D. (1977). "A study of chemi-ionization in the reaction of oxygen atoms with acetylene". The Journal of Physical Chemistry. 81 (23): 2137–2143. doi:10.1021/j100538a001. ISSN 0022-3654.
  12. ^ Fontijn, A.; Miller, W.J.; Hogan, J.M. (1965). "Chemi-ionization and chemiluminescence in the reaction of atomic oxygen with C2H2, C2D2, and C2H4". Symposium (International) on Combustion. 10 (1): 545–560. doi:10.1016/S0082-0784(65)80201-6. ISSN 0082-0784.
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