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The present work is devoted to the crystal field analysis of trivalent chromium doped in SrAl 2 O 4 spinel in the frame of the exchange charge model of crystal field. Using the shell model and pair approximation, we optimize the geometric structure of the crystal. The approach enables the modeling of the crystal field parameters and thus calculates the energy level scheme of Cr 3+ ions in spinel SrAl 2 O 4 . The obtained results are compared with experimental data and discussed.

The synthesis of isomeric (SPMe2)(0PPh2)NH 1 and (OPMe2)(SPPh2)NH 2 from Li[HN(S)PR2] and R'2P(O)Cl, as well as of their K and Na salts, are presented. The compounds were characterized by means of IR and multinuclear NMR spectroscopy. The crystal and molecular structure of both free acids was determined using X-ray diffractometry. Compound 1 crystallizes in monoclinic space group P2,/n, a = 16.798 (6) 8,. b = 17..526(8) A, c = 18.095(7) A, p =114.72(2)", Z = 12, and the unit cell contains three independentemolecules. Com ound 2 crystallizes in orthorhombic space group Fdd2, a = 1.5.072(7) A, b = 43.078(6) 1 c = 9.912(8) 8,. Z = 16. In both compounds the molecular units are associated into polymeric chains through N-H.-O l1.96 8, (mean) in 1, and 1.8 8, in 21 hydrogen bonds, which involve only the oxygen atom of each molecule. The conformation of the SPNPO system is discussed.

Zinc aluminate (ZnAl 2 O 4 ) doped with rare earth metal ions has been investigated most frequently because of the unique luminescent properties resulting from its stability and high emission quantum yields. The present work is devoted to calculate the Judd-Ofelt parameters ) and , ( 6 4 2    of the trivalent europium doped in ZnAl 2 O 4 spinel, the quality factor (Q) and the branching ratio ) ( .