“…The parameters of the quadrupole Hamiltonians of the 9 Be and 27 Al nuclei in an emerald single crystal have been determined [10][11][12]; the quadrupole parameters of 9 Be and 27 Al in pure Be 3 Al 2 Si 6 O 18 crystals at room temperature were studied by Brown and Williams [11], who reported values of e 2 qQ/h ¼0.504 MHz and Z¼0.09 and e 2 qQ/h¼3.093 MHz and Z¼0, respectively. In addition, various electron paramagnetic resonance (EPR) studies of emerald have been reported, including an antiferromagnetic exchange coupling study [8], the spin-lattice relaxation of Cr 3 + EPR at 22.2 GHz in the temperature range 1.5-45 K [13], a study of the EPR line-widths of the inter-doublet [14], and Cr 3 + and Fe 3 + EPR studies [15][16][17].…”