DOUBLE-ELECTRON CAPTURE PROCESS IN C3-H-2 COLLISIONS INFERRED FROM SPECTROSCOPIC MEASUREMENTS IN PLASMAS()

Pulsed Hp gas was injected into a carbon doped helium plasma in TPD-II to investigate electron capture processes. Anomalous enhancement in C II line intensities was observed and considered to be due to the doub le electron capture in C3+-H-2 collisions. The rate coefficient was es timated to be (3 +/- 2) x 10(-8) cm(3) s(-1), and a spectral distribut ion of C II lines, which relates to population densities of product C ions, was also measured. Based on these results, C II spectral distri butions in the JIPP T-IIU tokamak were observed to assess the influenc e of the double electron capture in C3+-H-2 collisions on the edge pla sma. A new spectroscopic procedure showed that this process is one of the dominant processes in the edge plasma.