EPR and optical absorption studies of VO2+ ions in L-asparagine monohydrate

Electron paramagnetic resonance (EPR) studies of VO2+ ions in L-asparagine monohydrate single crystals are reported at room temperature. It is found that the VO2+ ion takes up an interstitial site. The angular variations of the EPR spectra in three mutually perpendicular planes are used to determine the principal g and A values and their direction cosines. The values of g and A parameters are: g(x) = 1.9011, g(y) = 2.1008, g(z) = 1.9891 and A(x) = 100, A(y) = 78, A(z) = 126 (x 10(-4)) cm(-1). The optical absorption spectrum of VO2+ ions in L-asparagine monohydrate is also studied at room temperature. The band positions are calculated using the energy expressions and compared with the observed band positions to confirm the transitions. The best-fit values of the crystal field (Dq) and tetragonal (Ds and Dt) parameters are evaluated from the observed band positions. (c) 2007 Elsevier Ltd. All rights reserved.