Electron paramagnetic resonance spectrum of the GAMMA8 ground state of Np4+ diluted in Cs2ZrCl6

The electron-paramagnetic-resonance spectrum of Np4+ diluted in CsZrCl6 is analyzed in terms of the theory formulated by Belorizky et al. It is shown that if g/sub J/, the Lande g factor, is allowed to vary freely, a satisfactory fit may be obtained which is consistent with optical and EPR data obtained earlier on other tetrapositive actinide ions in the same host crystal. It is suggested that a better fit between the experimental data and the calculated spectrum may be obtained if the Zeeman mixing between the ground GAMMA8 state and the excited GAMMA6 state is considered