Talk:Direct analysis in real time

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Above undated message substituted from Template:Dashboard.wikiedu.org assignment by PrimeBOT (talk) 19:33, 16 January 2022 (UTC)

Questionable negative Ion formation process
I deleted the section about the negative ion formation process because the mechanism will not work as proposed in the article (M* + surface ---> M+   + surface  + e-). If in this case the He metastable (denoted as M) has an energy of 19.8 eV. The ionization potential of He is 25 eV. Thus in order to get the excited He into an ionized state(denoted as M+) you would have to let it collide with the surface with at least 5.2 eV....this is under these conditions not possible, because this kinetic energy would correspond to a velocity of around 15500 m/s (approx. mach 45)!

--Stomnerd (talk) 05:22, 23 May 2010 (UTC)


 * How about M* + surface ---> M + surface  + e- (surface Penning ionization)? See ; the other reactions then follow.  --Kkmurray (talk) 04:55, 24 May 2010 (UTC)

--Rbcody (talk) 18:13, 24 May 2018 (UTC) The negative-ion formation process was actually correct in the first place. The kinetic energy of the metastable atom does not play a role. This is surface Penning ionization, not collisional ionization of He*. Surface Penning ionization involves the release of an electron from the surface metal upon interaction with an excited state. The ionization energy of Molybdenum, the metal typically used for the DARt exit electrode, is 7.09 eV. Surface Penning ionization is well known, and it is the basis for a form of surface analysis by detecting the energy of electrons released upon bombardment by metastable atoms.

DART ion source
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DART ion source
I am planning to improve this article by adding and changing the content relevant to the italicized points. 1)Principle of operation   1.1 Basis DART setup and concept    1.2 Ionization process[Negative ion formation with detail, Reaction zone and interface]    1.3 Formation of metastable species 2)Source to analyzer interface 3)Mass spectra   3.1 Mass range and Gas temperature 4) ''Configurations of DART 4.1 Surface desorption mode 4.2 Transmission mode'' 5) Categorizing DART 6)Applications[Coupling with separation techniques, Quantification, Aerosol analysis]