Ionization and Excitation in Mercury Vapor Produced by Electron Bombardment

Abstract

The experimental determination of ionization and excitation in mercury vapor has been accomplished with an apparatus which permitted the evaluation of the electron energy from an accurately known magnetic field and the dimensions of the ion chamber. As a test of the apparatus the value of $\frac{e}{m}$ for the electron was measured and found to be 1.758×${10}^7$ e.m.u. A brief discussion of secondary emission and related effects is given. The ionization probability function is shown to have two important maxima, the first being at 10.8 volts and the second at 32 volts. The detailed structure between 10.4 volts and 16 volts indicates the composite character of the ionization function while the general smooth trend of the curve above 16 volts suggests that the process is relatively free from complication for high energy electrons. The study of photoelectric currents produced yielded new data on the electronic excitation function of the $2^{3}P_1^{}{}_{}{}^0$, $3^{3}P_1^{}{}_{}{}^0$, and $4^{3}P_1^{}{}_{}{}^0$ levels of the mercury atom showing that these have maxima in their probability functions at 5.6, 8.9, and 9.6 volts.