Sources
open directory project
Help build the largest human-edited directory on the web.
Submit a site - Become an editor
Wikipedia. Licensed under the GNU Free Documentation License.
Are you an expert in this subject? Join the discussion and share your knowledge at Wikipedia.org.
Thermal ionisation
From Wikipedia, the free encyclopedia
In Thermal Ionisation, also referred to as Surface Ionisation, chemically-purified material loaded onto a filament which is then heated may cause some of the loaded element to be ionized as it boils off the hot filament.
The likelihood of ionisation is a function of the filament temperature, the work-function of the filament substrate and the ionization energy of the element.
This is summarised in the Saha-Langmuir equation:
(Y1/Y0) = (g1/g0) exp [(WF-IP)/kT]
Y1/Y0 = ion to neutral ratio g1,g0 = statistical weights of ion and neutral states WF = Surface Work Function IP = element Ionisation Potential k = Boltzmann's constant T = surface temperature
One application of thermal ionisation is Thermal Ionisation Mass Spectrometry (TIMS). The ions coming of the filament are directed into a mass spectrometer to analyse the elements or isotopes present in the sample.