Relaxation processes in Nd are studied. We find that resonance coupling between Nd and other rare earth ions seems to exist. Nd plus Yb in Na<sub>0.5</sub>Gd<sub>0.5</sub>WO<sub>4</sub> results in a coupled system in which the Yb may be caused to fluoresce by pumping the Nd. Radiation trapping is found to play only a minor role.
G. E. PETERSON and P. M. BRIDENBAUGH, "Study of Relaxation Processes in Nd Using Pulsed Excitation," J. Opt. Soc. Am. 54, 644-646 (1964)