Paramagnetic Resonance of I2− Centers in PH4I Single Crystals

The I2− centers have been produced by x irradiation of PH4 crystals at liquid-nitrogen temperature and have been studied by electron paramagnetic resonance. The molecular axes of the centers were inclined 14.4° from the (001) plane, as might be expected from the crystal structure of PH4I. Constants of the spin Hamiltonian of I2− in PH4I have been determined to be G‖ = 1.901, g⊥ = 2.28, A‖ = 364 G, A⊥ = 73 G, and | Q′ | = 68 G. From this data the admixture of Πu2 wavefunction into the Σu+2 ground state of I2− is estimated to be about 15%.