EPR and optical study of Mn2+ doped L-asparagine monohydrate

The EPR spectrum of Mn2+ doped L-asparagine monohydrate at 77 K is analyzed and Mn2+ site entered in the lattice is discussed. The values of the zero field parameters providing good fit to the observed EPR spectra are determined. The evaluated g  , AA, BB, D, E and a values are 2.0912±0.0002, 98±2×10−4 cm−1, 91±2×10−4 cm−1, 299±2×10−4 cm−1, 99±2×10−4 cm−1 and −28×10−4 cm−1, respectively. The percentage covalency of the metal–ligand bond is also estimated. From the optical absorption at room temperature, the distortion in the lattice is suggested. The observed bands are assigned as transitions from the 6A1g(S) ground state to various excited quartet states of Mn2+ ion in a cubic crystalline field. The electron repulsion parameters (B and C), crystal field parameter (Dq) and Tree's correction (α) giving good fit to the observed optical spectra are evaluated and the values obtained for the parameters are B=767 cm−1, C=3032 cm−1, Dq=750 cm−1 and α=76 cm−1.