Optogalvanic spectroscopy

Optogalvanic spectroscopy is used for three purposes by rough classification: namely, plasma diagnosis such as the measurement of electric fields and the measurement of the spatial distribution of molecular density in plasma, spectroscopic utilization such as the research on atoms, molecules, radicals and molecular ions (hereafter, referred to as molecular species) in electron excitation state, and the detection of trace elements. Explanation is made placing emphasis on the first purpose and adding also the second purpose. As for the plasma diagnosis, the optogalvanic spectroscopy does not require the installation of a special detector. Irradiating laser beam to plasma and monitoring the electric characteristics of the plasma, the signals are obtained. It is a demerit that the electric noise of plasma is apt to exert effect. The principle of the measurement of optogalvanic effect, the method of measuring plasma using continuous emission laser and pulse laser, the examples of measurement as plasma diagnosis of electric fields, the threshold value of sputtering and the detection of minute amount in low pressure plasma, the spectrometry of CO molecules and so on are reported. (K.I.)