Editing Ion source (section)

==Desorption ionization==

===Field desorption===
{{Main|Field desorption}}
[[File:Field desorption.gif|thumb|300px|Field desorption schematic]]
Field desorption refers to an ion source in which a high-potential electric field is applied to an emitter with a sharp surface, such as a razor blade, or more commonly, a filament from which tiny "whiskers" have formed.<ref>{{cite journal | last1 = Beckey | first1 = H.D. | date =1969 | title = Field ionization mass spectrometry |journal=Research/Development | volume = 20 | issue = 11| page = 26 }}</ref>  This results in a very high electric field which can result in ionization of gaseous molecules of the analyte.  Mass spectra produced by FI have little or no fragmentation.  They are dominated by molecular radical cations {{chem2|M^{+.} }} and less often, protonated molecules {{chem2|[M + H]+}}

===Particle bombardment===

====Fast atom bombardment====
{{Main|fast atom bombardment}}
Particle bombardment with atoms is called fast atom bombardment (FAB) and bombardment with atomic or molecular ions is called [[secondary ion mass spectrometry]] (SIMS).<ref name="WilliamsFindeis1987">{{cite journal|last1=Williams|first1=Dudley H.|last2=Findeis|first2=A. Frederick|last3=Naylor|first3=Stephen|last4=Gibson|first4=Bradford W.|title=Aspects of the production of FAB and SIMS mass spectra|journal=Journal of the American Chemical Society|volume=109|issue=7|date=1987|pages=1980–1986|issn=0002-7863|doi=10.1021/ja00241a013|bibcode=1987JAChS.109.1980W }}</ref> Fission fragment ionization uses ionic or neutral atoms formed as a result of the [[nuclear fission]] of a suitable [[nuclide]], for example the [[Californium]] isotope <sup>252</sup>Cf.

In FAB the analytes is mixed with a non-volatile chemical protection environment called a [[Matrix Isolation|matrix]] and is bombarded under vacuum with a high energy (4000 to 10,000 [[electron volts]]) beam of atoms.<ref name="pmid7306100">{{cite journal |vauthors=Morris HR, Panico M, Barber M, Bordoli RS, Sedgwick RD, Tyler A | title = Fast atom bombardment: a new mass spectrometric method for peptide sequence analysis | journal = Biochem. Biophys. Res. Commun. | volume = 101 | issue = 2 | pages = 623–31 | date = 1981 | pmid = 7306100 | doi =10.1016/0006-291X(81)91304-8 }}</ref> The atoms are typically from an inert gas such as [[argon]] or [[xenon]]. Common matrices include [[glycerol]], [[thioglycerol]], [[3-nitrobenzyl alcohol]] (3-NBA), [[18-crown-6]] ether, [[2-nitrophenyloctyl ether]], [[sulfolane]], [[diethanolamine]], and [[triethanolamine]]. This technique is similar to secondary ion mass spectrometry and plasma desorption mass spectrometry.

====Secondary ionization====
{{Unreferenced section|date=October 2024}}
Secondary ion mass spectrometry (SIMS) is used to analyze the composition of solid surfaces and thin films by sputtering the surface of the specimen with a focused primary ion beam and collecting and analyzing ejected secondary ions. The mass/charge ratios of these secondary ions are measured with a mass spectrometer to determine the elemental, isotopic, or molecular composition of the surface to a depth of 1 to 2&nbsp;nm.

In a [[liquid metal ion source]] (LMIS), a metal (typically [[gallium]]) is heated to the liquid state and provided at the end of a capillary or a needle. Then a [[Taylor cone]] is formed under the application of a strong electric field. As the cone's tip get sharper, the electric field becomes stronger, until ions are produced by field evaporation. These ion sources are particularly used in [[ion implantation]] or in [[focused ion beam]] instruments.

====Plasma desorption ionization====
[[File:pdms inst.gif|thumb|300px|Schematic representation of a plasama desorption time-of-flight mass spectrometer]]
Plasma desorption ionization mass spectrometry (PDMS), also called fission fragment ionization, is a mass spectrometry technique in which ionization of material in a solid sample is accomplished by bombarding it with ionic or neutral atoms formed as a result of the [[nuclear fission]] of a suitable [[nuclide]], typically the [[californium]] isotope <sup>252</sup>Cf.<ref name="MacfarlaneTorgerson1976">{{cite journal|last1=Macfarlane|first1=R.|last2=Torgerson|first2=D.|title=Californium-252 plasma desorption mass spectroscopy|journal=Science|volume=191|issue=4230|date=1976|pages=920–925|issn=0036-8075|doi=10.1126/science.1251202|pmid=1251202|bibcode=1976Sci...191..920M}}</ref><ref name="Hilf1993">{{cite journal|last1=Hilf|first1=E.R.|title=Approaches to plasma desorption mass spectrometry by some theoretical physics concepts|journal=International Journal of Mass Spectrometry and Ion Processes|volume=126|date=1993|pages=25–36|issn=0168-1176|doi=10.1016/0168-1176(93)80067-O|bibcode=1993IJMSI.126...25H}}</ref>

===Laser desorption ionization===
{{Unreferenced section|date=October 2024}}
[[File:Maldi.PNG|thumb|300px|Diagram of a MALDI ion source]]
Matrix-assisted laser desorption/ionization (MALDI) is a soft ionization technique. The sample is mixed with a matrix material. Upon receiving a laser pulse, the matrix absorbs the laser energy and it is thought that primarily the matrix is desorbed and ionized (by addition of a proton) by this event. The analyte molecules are also desorbed. The matrix is then thought to transfer proton to the analyte molecules (e.g., protein molecules), thus charging the analyte.

====Surface-assisted laser desorption/ionization====
Surface-assisted laser desorption/ionization (SALDI) is a [[soft laser desorption]] technique used for analyzing [[biomolecule]]s by [[mass spectrometry]].<ref name="SunnerDratz1995">{{cite journal|last1=Sunner|first1=Jan.|last2=Dratz|first2=Edward.|last3=Chen|first3=Yu-Chie.|title=Graphite surface-assisted laser desorption/ionization time-of-flight mass spectrometry of peptides and proteins from liquid solutions|journal=Analytical Chemistry|volume=67|issue=23|date=1995|pages=4335–4342|issn=0003-2700|doi=10.1021/ac00119a021|pmid=8633776}}</ref><ref name="DattelbaumIyer2006">{{cite journal|last1=Dattelbaum|first1=Andrew M|last2=Iyer|first2=Srinivas|title=Surface-assisted laser desorption/ionization mass spectrometry|journal=Expert Review of Proteomics|volume=3|issue=1|date=2006|pages=153–161|issn=1478-9450|doi=10.1586/14789450.3.1.153|pmid=16445359|s2cid=39538990|url=https://zenodo.org/record/1235756|type=Submitted manuscript}}</ref> In its first embodiment, it used [[graphite]] matrix.<ref name="SunnerDratz1995" /> At present, laser desorption/ionization methods using other [[inorganic]] matrices, such as [[nanomaterials]], are often regarded as SALDI variants. A related method named "ambient SALDI" - which is a combination of conventional SALDI with ambient mass spectrometry incorporating the [[DART ion source]] - has also been demonstrated.<ref name="ZhangLi2012">{{cite journal|last1=Zhang|first1=Jialing|last2=Li|first2=Ze|last3=Zhang|first3=Chengsen|last4=Feng|first4=Baosheng|last5=Zhou|first5=Zhigui|last6=Bai|first6=Yu|last7=Liu|first7=Huwei|title=Graphite-Coated Paper as Substrate for High Sensitivity Analysis in Ambient Surface-Assisted Laser Desorption/Ionization Mass Spectrometry|journal=Analytical Chemistry|volume=84|issue=7|date=2012|pages=3296–3301|issn=0003-2700|doi=10.1021/ac300002g|pmid=22380704}}</ref>

====Surface-enhanced laser desorption/ionization====
{{Main|Surface-enhanced laser desorption/ionization}}
Surface-enhanced laser desorption/ionization (SELDI) is a variant of MALDI that is used for the analysis of [[protein]] [[mixture]]s  that uses a target modified to achieve biochemical [[Receptor affinity|affinity]] with the analyte compound.<ref>{{cite journal |vauthors=Tang N, Tornatore P, Weinberger SR |title=Current developments in SELDI affinity technology |journal=Mass Spectrometry Reviews |volume=23 |issue=1 |pages=34–44 |date=2004 |pmid=14625891 |doi=10.1002/mas.10066|bibcode = 2004MSRv...23...34T }}</ref>

====Desorption ionization on silicon====
{{Main|Desorption ionization on silicon}}
Desorption ionization on silicon (DIOS) refers to laser desorption/ionization of a sample deposited on a porous silicon surface.<ref name="BuriakWei1999">{{cite journal|last1=Buriak|first1=Jillian M.|title=Desorption-ionization mass spectrometry on porous silicon|last2=Wei|first2=Jing|author-link3=Gary Siuzdak|last3=Siuzdak|first3=Gary|journal=Nature|volume=399|issue=6733|date=1999|pages=243–246|issn=0028-0836|doi=10.1038/20400|pmid=10353246|bibcode=1999Natur.399..243W|s2cid=4314372}}</ref>

====Smalley source====
A laser vaporization cluster source produces ions using a combination of laser desorption ionization and supersonic expansion.<ref name="Duncan2012">{{cite journal|last1=Duncan|first1=Michael A.|title=Invited Review Article: Laser vaporization cluster sources|journal=Review of Scientific Instruments|volume=83|issue=4|pages=041101–041101–19|date=2012|issn=0034-6748|doi=10.1063/1.3697599|pmid=22559508|bibcode=2012RScI...83d1101D}}</ref> The '''Smalley source''' (or '''Smalley cluster source''')<ref>{{cite book|title=Laser Ablation and Desorption|url=https://books.google.com/books?id=iWfddcv0quwC&pg=PA628|date=10 December 1997|publisher=Academic Press|isbn=978-0-08-086020-6|pages=628–}}</ref> was developed by [[Richard Smalley]] at [[Rice University]] in the 1980s and was central to the discovery of [[fullerene]]s in 1985.<ref name="Smalley1997">{{cite journal|last1=Smalley|first1=Richard|title=Discovering the fullerenes|journal=Reviews of Modern Physics|volume=69|issue=3|date=1997|pages=723–730|issn=0034-6861|doi=10.1103/RevModPhys.69.723|bibcode=1997RvMP...69..723S}}</ref><ref name="Johnston2002">{{cite book|author=Roy L. Johnston|title=Atomic and Molecular Clusters|url=https://books.google.com/books?id=pxztbPhmBeIC&pg=PA150|date=25 April 2002|publisher=CRC Press|isbn=978-1-4200-5577-1|pages=150–}}</ref>

====Aerosol ionization====
In [[aerosol mass spectrometry]] with time-of-flight analysis, micrometer sized solid aerosol particles extracted from the atmosphere are simultaneously desorbed and ionized by a precisely timed laser pulse as they pass through the center of a time-of-flight ion extractor.<ref>{{Cite journal | doi = 10.1016/0021-8502(94)00133-J | title = On-line chemical analysis of aerosols by rapid single-particle mass spectrometry | date = 1995 | author = Carson, P | journal = Journal of Aerosol Science | volume = 26 | pages = 535–545 | last2 = Neubauer | first2 = K | last3 = Johnston | first3 = M | last4 = Wexler | first4 = A | issue = 4 | bibcode = 1995JAerS..26..535C }}</ref><ref>{{Cite journal | doi = 10.1016/S0021-8502(00)90189-7 | title = Real time monitoring of size-resolved single particle chemistry during INDOEX-IFP 99 | date = 2000 | author = Guazzotti, S | journal = Journal of Aerosol Science | volume = 31 | pages = 182–183 | last2 = Coffee | first2 = K | last3 = Prather | first3 = K | bibcode = 2000JAerS..31..182G }}</ref>