Photomultiplier Work function

Photomultipliers. In photomultipliers, the external photoelectric effect is utilized. Photons incident on a photocathode, which have an energy greater than the work function of cathode material expel electrons, which are captured by an anode that is positively charged relative to the cathode. The number of electrons produced is proportional to light intensity. They can be measured by the current flowing between electrodes. 

Photoemissive detectors, such as the photocell or the photomultiplier, are based on the external photoeffect. The photocathode of such a detector is covered with one or several layers of materials with a low work function (e.g., alkali metal compounds or semiconductor compounds). Under illumination with monochromatic light of wavelength x = c/v the emitted photoelectrons leave the photocathode with a kinetic energy given by the Einstein relation... 

Accordingly, from the photomultiplier signal the number of analyte atoms brought from a given amount of sample into the radiation source can be calculated directly. As all constants in the calculation shown, however, are not known apriori, AES in practice is a relative method and a calibration has to be performed. The determination of the calibration function is an important part of the working procedure. The calibration function relates the intensity of a spectral line (I) to the concentration c of an element in the sample. From the work of Scheibe [336] and Lomakin [337] the following relationship between absolute intensities and elemental concentrations was proposed ... 

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