Measurement of the Depopulation of the2P0,1,23Levels of Heliumlike Ions by Electron Collisions

The collisional depopulation rate of the $2{}_{}{}^3{}_{}{}^{}P_{0,1,2}^{}{}_{}{}^{}$ triplet levels of Cv, Nvi, Ovii, Fviii, and Ne ix was determined from measured $2{}_{}{}^3{}_{}{}^{}S-2\mathrm{}{}_{}{}^3{}_{}{}^{}P$ line intensity ratios. The triplet lines were observed in a hot $\theta$-pinch deuterium plasma seeded with a few percent of the element to be examined. The plasma electron temperature and density were known from laser-light-scattering experiments. The total depopulation rate of the $2{}_{}{}^3{}_{}{}^{}P_{0,1,2}^{}{}_{}{}^{}$ levels is mainly due to the $2{}_{}{}^3{}_{}{}^{}S-2\mathrm{}{}_{}{}^3{}_{}{}^{}P$ collisional deexcitation rate. The measured rate agrees well with calculations by Blaha based on the Coulomb—Born approximation. With these depopulation rates known, the electron density of the plasma can be determined just by measuring the triplet-line intensity ratios.