THE CONTACT POTENTIAL DIFFERENCE

The energy Ep, referenced to the vacuum level of the analyzer's grounded electrode, can be expressed in the following form:

(5.1.1)

where - is the contact potential difference between the cathode and the analyzer's grounded electrode,
k - Boltzman's constant,
Ò - cathode's temperature.

The contact potential difference is unsufficiently determined quantity, since it changes during spectrometer operation due to adsorption and desorption processes on the electrodes surfaces. This uncertainty gives the major contribution to the Ep error. The later is not higher than 1 eV for the spectrometers with tungsten cathodes and stainless steel analyzers [Ref 9].