A method for the analysis of thermal-pulse experiments is developed. An approximation for the electric-field distribution is calculated from the thermal-pulse data in a simple way, avoiding mathematical instabilities. The heart of the method is a set of appropriately constructed differential operators. It is shown that the thermal-pulse-response equation is exactly solved by the application of these differential operators. The application of the first-order differential operator suffices to reconstruct to a very good approximation the field distributions within electrets containing space charges or dipoles. The method of analysis is especially suitable for the probing of electric-field distributions near the sample surface. Furthermore, the technique allows an on-line analysis of thermal-pulse data. The merit of the method is demonstrated with measured thermal-pulse data obtained with a negatively corona-charged Teflon polyfluoroethylene propylene sample and with an electron-beam-charged Teflon sample. Additionally, the thermal diffusivity of the electret film is measurable with the thermal-pulse technique if the field distribution within the sample is known.
