Measurement of Negative Ions by Photodetachment with YAG Laser in Discharge Plasmas

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Abstract
The photodetachment response of neagative ions has been investigated with YAG lasers using a hollow cathode discharge in oxygen. The current of electrons released by the laser has been measured as a function of the discharge current and the pressure. The diagnostic method is formulated in such a manner that the densities of atomic and molecular negative ions are determined simultaneously from the response of photodetached electrons to the fundamental and second harmonic radiation of YAG laser. The sum of the densities compares well with the total negative ion density obtained by the probe method.