Electron paramagnetic resonance ofPu3+andCf3+in single crystals ofLuPO4

Abstract

Electron-paramagnetic-resonance (EPR) spectroscopy has been used to investigate the ground-state properties of the actinide ions Pu[sup 3+] (5[ital f][sup 5]) and Cf[sup 3+] (5[ital f][sup 9]) incorporated as dilute impurities in single crystals of the tetragonal-symmetry host LuPO[sub 4]. The [ital g] values of the electronic ground states were determined experimentally at a sample temperature of 4 K. These values are compared to those calculated using the free-ion parameters available from previous crystal-field analyses of Pu[sup 3+] and Cf[sup 3+] ions diluted in LaCl[sub 3]-host single crystals and a set of crystal-field parameters reported earlier for Cm[sup 3+] (5[ital f][sup 7]) ions in LuPO[sub 4]. These crystal-field parameters were obtained from spin-Hamiltonian parameters using operator-equivalent factors and the assumption that the zero-field splitting of the ground state of the 5[ital f][sup 7] ion is due primarily to intermediate-coupling effects. The relatively poor agreement between the experimental and calculated [ital g] values indicates that the crystal-field parameters obtained for Cm[sup 3+] in LuPO[sub 4] cannot be used to predict the correct electronic ground-state properties of the other actinide ions Pu[sup 3+] and Cf[sup 3+] in the identical host single-crystal LuPO[sub 4]. Accordingly, in the case of actinide impurity ions in singlemore » crystals, there is no simple correspondence between the spin-Hamiltonian parameters and the crystal-field parameters.« less