The population of the 4p sublevel of the excited hydrogen atom produced through dissociation of a molecule was determined by analyzing its observed radiative decay curve in the earlier literature. In electron-impact experiments,however,it is difficult to prepare a pulsed electron beam with a pulse duration of several nanoseconds at low energy. We have newly developed a method for obtaining the population of the 4p sublevel,using a photon-photon coincidence technique with a continuous electron beam,and applied this technique to trifluoromethane and methane. |