When molecular motion occurs on multiple timescales, interpreting deut
eron Zeeman relaxation times, T-1Z, yields ambiguous results, Simultan
eous measurements of the orientation dependence of T-1Z and the quadru
pole order relaxation time, T-1Q, are required to provide a more accur
ate description. Processes with microsecond correlation times necessit
ate analysis based on the stochastic Liouville equation. Relaxation of
methyl deuterated bisphenol-A polycarbonate is considered as an illus
tration, Numerous Redfield models are consistent with the T-1Z data, b
ut their failure to reproduce the observed T-1Q anisotropy is characte
ristic of slow motion. In complex systems where slow motion is ubiquit
ous, it is essential that motional studies include measurement of both
T-1Z and T-1Q anisotropies.