Work Function

This is the energy required to remove an electron from the highest filled level in the Fermi distribution of a solid to a point a long way away, at absolute zero.
I = thermionic current [A]
T = temperature [K]
φ = work function [eV]
A = constant with a theoretical value of 120 Acm-2K-2
k = Boltzmannís constant = 1.38062x10-23 JK-1

In ion engines, the work function of the ionizer must be greater than the ionization potential of the neutral atoms in the propellant gas.

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Subjects: Physics