Achievement of Ultimate Performances of Laser Spectroscopic Methods for Measurements of Electric Fields in Plasmas and Gases

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This research has been carried out to achieve ultimate performances of laser spectroscopic methods for measurements of electric fields in plasmas and gases ; namely (i) to facilitate measurements of electric fields in glow discharge plasmas constituting not only He but other atoms such as Ar, and (ii) to pursue possibility of electric field measurements in atmosphere. There have been great demands for these measurements.Obtained results are as follows.1. The first spectroscopic study of the Stark effect for Ar atoms has been conducted, and yielded very useful information. This includes the clarification of Rydberg levels which are sensitive to electric fields, and of the relationship between the electric fields and the amounts of Stark shifts (the second article in the item 11 below).2. It has been shown that the direction of an electric field can be decided by the use of the polarization of a laser (the third article in the item 11 below).3. Applicable ranges of the two-step laser induced fluorescence have been clarified, especially for atoms such as He and Ar.4. In order to measure electric fields under thunderclouds and in barrier discharges in atmosphere, the three photon excitation of Ar atoms, which is the key technology for the development, has been tested. The results have yielded the levels which are easily populated, thus enabled future developments.