Study on the variation of current signal intensity in Franck-Hertz experiment

In the Franck-Hertz experiment,the intensity of Ip-V varies with the temperature of the oven and the voltage of the filament.We find that the intensity of Ip-V signal decreases with the temperature when the temperature is below 160 ℃,and increases with the temperature when the temperature is higher than 170 ℃.We then introduce the model of thermal excitation and ionization,which explains such phenomenon when the law of thermal-dynamic equilibrium and the Le Chteler's law are applied.After that,we have designed some additional experiments,whose results support our postulation.