Relaxation times and line widths of isotopically-substituted nitroxides in aqueous solution at X-band

► Six nitroxides were studied at X-band in the rapid tumbling regime. ► T1 and T2 were measured by pulse methods and CW linewidths were simulated. ► T1 and T2 are longer for 15N than for 14N and are dependent on mI. ► Relaxation times at low frequency are predicted to be similar to values at X-band.