Accumulated photon echoes were used to measure 1-800 ps dephasing time
s (T2) for the I-4(9/2) --> 4G5/2, 2G7/2G7/2 transition of Nd3+ ions l
ocated in two different symmetry sites in highly disordered CaF2-YF3 c
rystals. The temperature dependence of 1/(piT2) from 9-100 K is descri
bed by a single phonon absorption process.