Gas-phase ion chemistry
Gas phase ion chemistry is a field of science encompassed within both
Theory
Transition state theory
Transition state theory is the theory of the rates of elementary reactions which assumes a special type of chemical equilibrium (quasi-equilibrium) between reactants and activated complexes.[3]
RRKM theory
RRKM theory is used to compute simple estimates of the
Gas phase ion formation
The process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions can occur in the gas phase. These processes are an important component of gas phase ion chemistry.
Associative ionization
Associative ionization is a gas phase reaction in which two atoms or molecules interact to form a single product ion.[4]
where species A with excess internal energy (indicated by the asterisk) interacts with B to form the ion AB+.
One or both of the interacting species may have excess internal energy.
Charge-exchange ionization
Charge-exchange ionization (also called charge-transfer ionization) is a gas phase reaction between an ion and a neutral species
in which the charge of the ion is transferred to the neutral.[5]
Chemical ionization
In chemical ionization, ions are produced through the reaction of ions of a reagent gas with other species.[6] Some common reagent gases include: methane, ammonia, and isobutane.
Chemi-ionization
Chemi-ionization can be represented by
where G is the excited state species (indicated by the superscripted asterisk), and M is the species that is ionized by the loss of an
Penning ionization
Penning ionization refers to the interaction between a gas-phase excited-state atom or molecule G* and a target molecule M resulting in the formation of a radical molecular cation M+., an electron e−, and a neutral gas molecule G:[7]
Penning ionization occurs when the target molecule has an
Fragmentation
There are many important dissociation reactions that take place in the gas phase.
Collision-induced dissociation
CID (also called collisionally activated dissociation - CAD) is a method used to fragment molecular ions in the gas phase.[8][9] The molecular ions collide with neutral gas molecules such as helium, nitrogen, or argon. In the collision some of the kinetic energy is converted into internal energy which results in fragmentation.
Charge remote fragmentation
Charge remote fragmentation is a type of covalent bond breaking that occurs in a gas phase ion in which the cleaved bond is not adjacent to the location of the charge.[10][11]
Charge transfer reactions
There are several types of charge-transfer reactions[12] (also known as charge-permutation reactions[13]): partial-charge transfer
- ,
charge-stripping reaction[14]
- ,
and charge-inversion reaction[15] positive to negative
and negative to positive
- .
Applications
Pairwise interactions between alkali metal ions and amino acids, small peptides and nucleobases have been studied theoretically in some detail.[16]
See also
- Adiabatic ionization
- Mass-analyzed ion kinetic energy spectrometry
- Plasma (physics)
- Michael T. Bowers
- R. Graham Cooks
- Helmut Schwarz
References
- .
- ^ Pure & Appl. Chem., Vol. 70, No. 10, pp. 1969–1976, 1998.
- ^ Munson, M.S.B.; Field, F.H. J. Am. Chem. Soc. 1966, 88, 2621-2630. Chemical Ionization Mass Spectrometry. I. General Introduction.
- )
- PMID 15481084.
- PMID 11199379.
- .
- PMID 26860300.
Bibliography
- Fundamentals of gas phase ion chemistry, Keith R. Jennings (ed.), Dordrecht, Boston, Kluwer Academic, 1991, pp. 226–8
- Gas Phase Ion Chemistry, Michael T. Bowers, ed., Academic Press, New York, 1979
- Gas Phase Ion Chemistry Vol 2.; Bowers, M.T., Ed.; Academic Press: New York, 1979
- Gas Phase Ion Chemistry Vol 3., Michael T. Bowers, ed., Academic Press, New York, 1983