EPR and optical absorption studies on VO2+ ions in l-asparagine monohydrate single crystals

Abstract: X-Band electron paramagnetic resonance (EPR) studies of VO2+ ions in l-asparagine monohydrate single crystals have been done at room temperature. Detailed EPR analysis indicates the presence of two magnetically inequivalent VO2+ sites. Both the vanadyl complexes are found to take up interstitial position. The angular variation of the EPR spectra in three planes ab, bc and ca are used to determine principal g and A tensors. For the two sites the spin Hamiltonian parameters are, site I: g x =1.9633, g y =2.0274, g z =1.9797, A x =88, A y =61, A z =161×10−4 cm−1; site II: g x =1.9627, g y =1.9880, g z =1.9425, A x =90, A y =66, A z =167×10−4 cm−1. The optical absorption study is also carried out at room temperature and absorption bands are assigned to various transitions. The theoretical band positions are obtained using energy expressions and a good agreement is found with the experimental values. By correlating EPR and optical data different molecular orbital coefficients are evaluated and the nature of bonding in the crystal is discussed. [Copyright &y& Elsevier]