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In this work, the complete matrix of optical spectral levels in trigonal symmetry of 3d(2) (3d(8)) ions are established on basis of strong field coupling mechanism by using two spin-orbit coupling parameters model. The contribution of the spin-orbit coupling of ligand to the optical spectra has been included in these formulas. As an application, the optical spectra of Cr4+ in Y2Ti2O7 and Y2Sn2O7 have been studied by the complete diagonalization (energy matrix) method. The covalent effect has been studied and the difficulty about Dq parameter in explanation of optical spectra of Cr-doped Y2Ti2O7 and Y2Sn2O7 is removed. The theoretical results are in good agreement with observed data. (C) 2012 Elsevier B.V. All rights reserved.