Excitation equilibrium for low lying levels in Cii,Niii, Oiv,Nevi, Mgviii,Six, and Siii

The populations of the excited state ²P_3/2 relative to the ground state ²P_1/2 have been investigated in C ii, N iii, O iv, Ne vi, Mg viii, Si x, and Si ii by considering all the radiative and collisional processes including the collisional transitions to the higher states which cascade to the upper level. The relative populations are used for the calculation of the line emissivities. The intensities of 76 320, 30 258 and 14 302 lines of Nevi, Mgviii, and Six ions respectively in the chromosphere-corona transition region are also calculated.