ELECTRON-PARAMAGNETIC-RESONANCE AND MOLECULAR-ORBITAL STUDY OF CO-3(-) IONS ENTRAPPED IN KCL SINGLE-CRYSTALS

Two different CO3- ions are detected in KCl single crystals by means o f electron paramagnetic resonance (EPR). The spin Hamiltonian of the f irst ion exhibits orthorhombic symmetry whereas the other CO3- is rapi dly rotating around a [001] axis and hence has axially symmetric spin Hamiltonian parameters. Theoretical calculations using both the CNDO/I I and INDO methods were performed in order to reproduce and understand the experimentally obtained spin Hamiltonian parameters for the ortho rhombic defect. In this way, the different principal values of the g a nd C-13 hyperfine tensors could be assigned to the distinct molecular axes, yielding the model for the orthorhombic CO3- radical in KCl.