Multifrequency electron paramagnetic resonance spectroscopy on oriented single crystals of magnetically dilute Gd(III) ions in Gd0.004Y0.996(trensal) is used to determine the Hamiltonian parameters of the ground (8)S(7/2 )term and its phase memory time, T-m, characterizing its coherent spin dynamics. The vanishing orbital angular momentum of the S-8(7/2) term makes it relatively insensitive to spin-lattice relaxation mediated by magnetoelastic coupling and leads to a T-m of 12 mu s at 3 K, which is not limited by spin-lattice relaxation.