The Thermionic Emission from Clean Platinum

Abstract

The thermionic emission from thoroughly outgassed platinum in high vacuum has been measured to one-half percent over the temperature range 1360 to 1750\ifmmode^\circ\else\textdegree\fi{}K, the temperatures being measured by careful optical pyrometry. The values obtained for the thermionic constants of the ${T}^{2}$ law are, when corrected for the Schottky effect, $b=72, 820\ifmmode^\circ\else\textdegree\fi{}$K, $\ensuremath{\varphi}=6.27$ volts, $A=17,000$ amp/${\mathrm{cm}}^{2}$ ${\mathrm{deg}}^{2}$. The value of $\ensuremath{\varphi}$ is possibly in error by not more than 1 percent because of uncertainties in the temperature scale, and agrees within one-half percent with the value of the photoelectric work function previously obtained. The data confirm the previous announcement that for clean platinum $A$ is 250 times greater than the theoretical value of 60.2 amp/${\mathrm{cm}}^{2}$ ${\mathrm{deg}}^{2}$.