EPR, optical, infrared and Raman studies of VO2+ ions in polyvinylalcohol films

Electron paramagnetic resonance (EPR), optical, infrared and Raman spectral studies have been carried out on vanadyl ions doped in polyvinylalcohol (PVA) films. The spin-Hamiltonian parameters (g and A) and the molecular orbital coefficients ($\beta_2^{*2} $ and k) have been evaluated. The values of spin-Hamiltonian parameters confirm that the vanadyl ions are present in PVA films as $VO^{2+}$ molecular ions in an octahedral site with a tetragonal compression $(C_{4V})$. The temperature variation EPR studies reveal that the variation of number of spins with temperature is in accordance with Boltzmann law. It is interesting to observe that the variation of susceptibility with temperature obeys Curie–Weiss law. The FT-IR and FT-Raman spectrum exhibits few bands, which are attributed to O–H, C–H, CQC and C–O groups of stretching and bending vibrations. The optical absorption spectrum exhibits two bands, which are assigned to $^2B_{2g}\rightarrow ^2B_{1g}$ and $^2B_{2g}\rightarrow ^2E_g$ transitions in the decreasing order of energy.