Thermal ionisation

Encyclopedia : T : TH : THE : Thermal ionisation

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.

From Wikipedia, the Free Encyclopedia. Original article here. Support Wikipedia by contributing or donating.
All text is available under the terms of the GNU Free Documentation License See Wikipedia Copyrights for details.