Abstract: Applying the Hooper's first-order theory, we have calculated the static micro-electric field distributions in plasmas containing various multiply-charged ions. The influences of the impurity concentrations on the microelectric field distributions and on the Lyman profiles (ⁿ→l)from hydrogenic ions have been analysed. Based on the optical-thin line profiles, the radiation transfer equation in sphere plasmas with various optical depths has been solved. The results confirm that the opacity-broadening of the line profiles has almost no effect on the seperation of Lyman ^β splitted peaks. Such seperation is determined by electric field at which the static micro-electric field distribution has a maximum. The seperation can be utilized for spatially resolved and temporally resolved density diagnostic of fusion plasmas.