Spectroscopy of the Solid State: Potassium and Calcium

Utilizing the techniques developed by O'Bryan and Skinner for the study of the emission bands of metals, it has been possible to determine the structure of the conduction bands of the metals, potassium and calcium. The spectrograph used utilizes a photomultiplier in place of a photograph plate, thus enabling higher sensitivity and ease of operation. The particular radiation studied is produced by transitions of the conduction electrons into the ionized $3p$ state of the atom. The limiting factor in the accuracy of the emission band obtained in this way is the purity of the sample studied. The contamination of the surface of an evaporated sample affects the resultant curve mainly as a result of insufficient penetration of the electrons, since the photon absorption is negligible at depths required to produce radiation representative of the pure bulk metal. The results for potassium and calcium at temperatures between 25\ifmmode^\circ\else\textdegree\fi{}C and 100\ifmmode^\circ\else\textdegree\fi{}C are not in good agreement with previous theoretical calculations. The experimental values of band width are 1.9 and 3.0 ev, respectively, compared with the theoretical calculations of 3.6 and 5.0 ev.