A nuclear magnetic resonance study of tetramethylammonium tribromocadmate

Proton spin lattice relaxation (T 1 ) in (CH 3 ) 4 NCdBr 3 at different Larmor frequencies (10, 20 and 30 MHz) has been studied in the temperature range 77 to 400 K. The variations in T 1 at high temperature are independent of frequency and show a maximum due to spin rotation-interaction. The other features are interpreted as being due to isotropic tumbling of the tetramethylammonium ion and random reorientation of the CH 3 group. The CW spectrum remained narrow up to 77 K and develops a wing structure at low temperatures. This observation is attributed to a possible tunnelling motion of the CH 3 group, which has rather low activation energy as demonstrated by the study of T 1 .