Introduction

The field called photoelectron ejection is phenomenologically no different that photoelectron spectroscopy. In both cases one uses a monochromatic source of photons to eject photoelectrons, thereby learning about electronic structure through data on binding energies. In photoelectron spectroscopy the interaction known as the photoelectric effect is primary importance, which was detected by Hertz in 1887. Einstein in 1905 was able to explain their systematics by involving the quantum nature of light by the Einstein relation,

The experiments at that time were performed as depicted in this figure. A monochromatic light obtained by a prism spectrograph was focused onto a surface of potassium or sodium in a vacuum tube. It resulted in the emission of an electron from that extranuclear cloud of core and valence electrons. The kinetic energy, E_kin, of the ejected electrons was determined by measuring the voltage required to suppress the current across the vacuum vessel. This means, in essence, that the potential energy supplied by the externally applied voltage equals the maximum kinetic energy, E_max,kin, of the photoejected electrons.

By performing such experiments as a function of the frequency of the light w, one was able to determine the ratio of Planck's constant to the electronic charge and also the work function f of the metal under study.

Where U is the retarding voltage, and E_max,kin is the maximum electron kinetic energy. The experiment, as illustrated in the first figure actually measures the difference of the work function, Df, of the anode and cathode. The work function of a particular material is obtained by measuring this difference for various combinations of materials.

Systematic data on U(w) for some metals are given in the accompanying figure. As expected, all lines have the same slope which, according to equation (1.1), is equal to (). The data for different metals are, however, displayed with respect to each other due to their different work functions.