On the instrument function of electrostatic electron spectrometers

The article critically analyses a conception of electron spectrometers instrument function. By means of a dimensionless mathematical model built here a strict defined integral correlation between a source energy spectrum and a current registered by detector in dependence of a device working energy is defined. It is proved that the instrument function always depends only on a ratio (E / U), but not a difference, and not an inverse ratio (U / E) as it is declared in some articles. The main integral equation built in the article is of Volterra equation of Ist type, but not one of Fredholm of Ist type. Some concrete structures of instrument function are calculated and presented in the article. Their common features are described and discussed.