EPR investigation of Eu2+ in orthorhombic sites of RbBr

Accurate spin-Hamiltonian parameters describing the electron paramagnetic resonance spectra of Eu2+ in orthorhombic sites of RbBr single crystals have been determined at 77 and 300 K for the first time. Absolute signs of the spin-Hamiltonian parameters were determined for sample temperatures less than 4.2 K. The sign of the spin-Hamiltonian parameter b20 was found to be positive and therefore the same as that previously found for the same impurity in the isomorphic hosts of NaBr and KBr. We present a plot of the b20 term vs lattice parameter for Eu2+ ions in the alkali bromide series with results which should be noted in attempts to calculate theoretical 8S7/2 ground state splittings.