The Energy Distribution of Photoelectrons Emitted by Calcium and Calcium Oxide

Measurements of the energy distribution of the photoelectrons emitted from calcium with the aid of a magnetic velocity analyzer using radiation of wave-length λ2536 have been made. Special care was taken to eliminate contact potentials and to ensure that the emission observed was that from pure calcium. Energy distribution curves were obtained for pure Ca, CaO, and for a number of stages intermediate between the oxide and the pure metal. The theories of Fowler, DuBridge, Mitchell, and Nottingham were found to compare favorably with the data for pure Ca on the high energy side, but to depart from the data at low energies. The photoelectric work function obtained for pure Ca was 3.21 electron volts. The failure of all attempts to fit the above theories to the data for the oxide indicates that the Sommerfeld theory of a metal is not applicable to CaO.