User:Eoneill8/sandbox

= Other Work =

Thermionic Emission

In the early 1920’s, Clinton Davisson published research regarding Thermionics, a natural phenomenon in which heating of a material results in a flow of charge carriers. Much of Davisson’s later work was devoted to this field. Davisson and Germer’s 1922 paper, entitled The Thermionic Work Function of Tungsten, discusses a means of calculating the characteristic work function (ψ₁)—energy required to emit an electron—for a tungsten wire. Results were acquired through two different experiments, so that they could be compared.

One method of measurement was known as the calorimetric method. Essentially, a tubular electrode was charged and a hot tungsten wire was placed inside. If the electrode was positively charged, a flow of electrons would be induced from the wire to the electrode. Interestingly, the induced emission of electrons caused a temperature decrease in the wire, which in turn lowered the resistance of the wire. As a result, a voltage drop between terminals of the wire could be measured. This method of measuring the work function of tungsten proved to be more accurate than a previously reported technique, which relied on variation of the metal’s temperature.

Davisson and Germer’s results by the calorimetric method differed slightly but significantly from those obtained by the accepted temperature variation method reported by O. W. Richardson. In assuming the thermal energy of emission to be effectively zero, Davisson found that the results could not be accurately described by Richardson’s classical model. Rather, he proposed an alteration of Richardson's theory. The new work function was described as follows

$\psi _{1}=\psi _{0}+{\frac {3}{2}}{\frac {k}{e}}\ T$ .

The new model was preferable because it no longer constrained voltage and temperature in a linear relationship, but still accounted for temperature variations in the term.