|
|
| Line 1: |
Line 1: |
| {{Use dmy dates|date=November 2012}}
| | The writer is known as Wilber Pegues. Her family lives in Ohio but her spouse desires them to transfer. Credit authorising is where my main earnings comes from. One of the extremely very best things in the globe for him is doing ballet and he'll be beginning something else alongside with it.<br><br>My blog post :: certified psychics ([http://cspl.postech.ac.kr/zboard/Membersonly/144571 http://cspl.postech.ac.kr/]) |
| '''Gas phase ion chemistry''' is a field of science encompassed within both [[chemistry]] and [[physics]]. It is the science that studies [[ion]]s and [[molecule]]s in the gas phase, most often enabled by some form of [[mass spectrometry]]. By far the most important applications for this science is in studying the [[thermodynamic]]s and [[chemical kinetics|kinetics]] of reactions.<ref name=Aubry2000>{{Cite journal | last = Aubry | first = C. | year = 2000 | title = Correlating thermochemical data for gas-phase ion chemistry | journal = International Journal of Mass Spectrometry | volume = 200 | issue = 1-3 | pages = 277 | doi = 10.1016/S1387-3806(00)00323-7 | postscript = <!--None-->}}</ref><ref>[http://www.iupac.org/publications/pac/1998/pdf/7010x1969.pdf Pure & Appl. Chem., Vol. 70, No. 10, pp. 1969-1976, 1998.]</ref> For example one application is in studying the [[thermodynamics]] of the [[solvation]] of ions. Ions with small [[solvation]] spheres of 1, 2, 3... solvent molecules can be studied in the gas phase and then extrapolated to bulk solution.
| |
| | |
| ==Theory==
| |
| | |
| ===Transition state theory===
| |
| {{Main|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.<ref>{{GoldBookRef|title=Transition State Theory|file= T06470}}</ref>
| |
| | |
| ===RRKM theory===
| |
| {{main|RRKM theory}}
| |
| RRKM theory is used to compute simple estimates of the [[unimolecular ion decomposition]] [[reaction rates]] from a few characteristics of the [[potential energy surface]].
| |
| | |
| ==Gas phase ion formation==
| |
| The process of converting an [[atom]] or [[molecule]] into an [[ion]] by adding or removing charged particles such as [[electron]]s or other ions can occur in the gas phase. These processes are an important component of gas phase ion chemistry.
| |
| | |
| ===Associative ionization===
| |
| {{main|Associative ionization}}
| |
| Associative ionization is a gas phase reaction in which two [[atom]]s or [[molecule]]s interact to form a single product [[ion]].<ref>{{GoldBookRef|title=associative ionization|file= A00475}}</ref>
| |
| | |
| :<math>A^* + B \to AB^{+\bullet} + e^-</math>
| |
| | |
| where species A with excess internal energy (indicated by the asterisk) interacts with B to form the ion AB<sup>+</sup>.
| |
| | |
| One or both of the interacting species may have excess [[internal energy]].
| |
| | |
| ===Charge-exchange ionization===
| |
| {{main|Charge-exchange ionization}}
| |
| Charge-exchange ionization (also called '''charge-transfer ionization''') is a gas phase reaction between an [[ion]] and a neutral species
| |
| :<math>A^+ + B \to A + B^+</math>
| |
| in which the charge of the ion is transferred to the neutral.<ref>{{GoldBookRef|title=charge-exchange ionization|file= C00989}}</ref>
| |
| | |
| ===Chemical ionization===
| |
| {{main|chemical ionization}}
| |
| In chemical ionization, ions are produced through the reaction of ions of a reagent gas with other species.<ref>Munson, M.S.B.; Field, F.H. ''J. Am. Chem. Soc.'' '''1966''', ''88'', 2621-2630. [http://dx.doi.org/10.1021/ja00964a001 Chemical Ionization Mass Spectrometry. I. General Introduction].</ref> Some common reagent gases include: [[methane]], [[ammonia]], and [[isobutane]].
| |
| | |
| ===Chemi-ionization===
| |
| {{main|Chemi-ionization}}
| |
| Chemi-ionization can be represented by
| |
| :<math>G^* + M \to M^{+\bullet} + e^- + G</math>
| |
| 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 [[electron]] to form the [[Radical (chemistry)|radical]] [[cation]] (indicated by the superscripted "plus-dot").
| |
| | |
| ===Penning ionization===
| |
| {{main|Penning ionization}}
| |
| Penning ionization refers to the interaction between a gas-phase excited-state atom or molecule G<sup>*</sup> and a target molecule M resulting in the formation of a radical molecular cation M<sup>+.</sup>, an electron e<sup>−</sup>, and a neutral gas molecule G:<ref>{{GoldBookRef|title=Penning gas mixture|file= P04476}}</ref>
| |
| | |
| :<math>G^* + M \to M^{+\bullet} + e^- + G</math> | |
| | |
| Penning ionization occurs when the target molecule has an [[ionization potential]] lower than the internal energy of the excited-state atom or molecule. [[associative ionization|Associative]] Penning ionization can also occur:
| |
| | |
| :<math>G^* + M \to MG^{+\bullet} + e^-</math>
| |
| | |
| ==Fragmentation==
| |
| There are many important [[Dissociation (chemistry)|dissociation]] reactions that take place in the gas phase.
| |
| | |
| ===Collision-induced dissociation===
| |
| {{main|Collision-induced dissociation}}
| |
| CID (also called collisionally activated dissociation - CAD) is a method used to fragment molecular [[ion]]s in the gas phase.<ref name="pmid16401509">{{cite journal |author=Wells JM, [[Scott A. McLuckey|McLuckey SA]] |title=Collision-induced dissociation (CID) of peptides and proteins |journal=Meth. Enzymol. |volume=402 |issue= |pages=148–85 |year=2005 |pmid=16401509 |doi=10.1016/S0076-6879(05)02005-7}}</ref><ref name="pmid15481084">{{cite journal |author=Sleno L, Volmer DA |title=Ion activation methods for tandem mass spectrometry |journal=Journal of mass spectrometry : JMS |volume=39 |issue=10 |pages=1091–112 |year=2004 |pmid=15481084 |doi=10.1002/jms.703}}</ref> 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===
| |
| {{main|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.<ref name="pmid11199379">{{cite journal |author=Cheng C, Gross ML |title=Applications and mechanisms of charge-remote fragmentation |journal=Mass Spectrom Rev |volume=19 |issue=6 |pages=398–420 |year=2000 |pmid=11199379 |doi=10.1002/1098-2787(2000)19:6<398::AID-MAS3>3.0.CO;2-B}}</ref><ref name=Gross2000>{{Cite journal | last = Gross | first = M. | year = 2000 | title = Charge-remote fragmentation: an account of research on mechanisms and applications | journal = International Journal of Mass Spectrometry | volume = 200 | issue = 1-3 | pages = 611 | doi = 10.1016/S1387-3806(00)00372-9 | postscript = <!--None--> }}</ref>
| |
| | |
| ==Charge transfer reactions==
| |
| There are several types of charge-transfer reactions<ref>{{GoldBookRef|title=charge-transfer reaction (in mass spectrometry)|file=C01005}}</ref> (also known as charge-permutation reactions<ref>{{GoldBookRef|title=charge-permutation reaction|file=M04002}}</ref>): partial-charge transfer
| |
| | |
| :<math>A^{2+} + B \to A^+ + B^+</math>,
| |
| | |
| charge-stripping reaction<ref>{{GoldBookRef|title=charge-stripping reaction|file=C01001}}</ref>
| |
| | |
| :<math>A^+ + B \to A^{2+} + B + e^-</math>,
| |
| | |
| and charge-inversion reaction<ref>{{GoldBookRef|title=charge-inversion mass spectrum|file=C00992}}</ref> positive to negative
| |
| | |
| :<math>A^+ + B \to A^- + B^{2+} </math>
| |
| | |
| and negative to positive
| |
| | |
| :<math>A^- + B \to A^+ + B + 2e^-</math>.
| |
| | |
| ==See also==
| |
| *[[Adiabatic ionization]]
| |
| *[[Mass-analyzed ion kinetic energy spectrometry]]
| |
| *[[Plasma (physics)]]
| |
| *[[Michael T. Bowers]]
| |
| *[[R. Graham Cooks]]
| |
| *[[Helmut Schwarz]]
| |
| | |
| == References ==
| |
| {{Reflist}}
| |
| | |
| ==Bibliography==
| |
| {{refbegin}}
| |
| *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
| |
| {{refend}}
| |
| | |
| ==External links==
| |
| * http://webbook.nist.gov/chemistry/ion/
| |
| | |
| [[Category:Mass spectrometry]]
| |
The writer is known as Wilber Pegues. Her family lives in Ohio but her spouse desires them to transfer. Credit authorising is where my main earnings comes from. One of the extremely very best things in the globe for him is doing ballet and he'll be beginning something else alongside with it.
My blog post :: certified psychics (http://cspl.postech.ac.kr/)