| Summary: | An average temperature coefficient of the work function of 167 UV/°K has been found for evaporated films of barium between 80°C and 280°C in vacua of less than 10-9 millimeters of mercury. The results show small but definite curvatures in the work function relationship. Experimental measurements were found to be reproducible, free from drift and free from temperature dependent contamination effects. The design and performance of apparatus employing the retarding field characteristics of a diode to measure changes in the work function has been evaluated. This apparatus, while not suited to measuring the absolute work function, has the advantage of providing a sensitive indication of changes in the work function. Existing theories of the temperature dependence of the work function are briefly reviewed and shown to be inadequate.
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