Field cycling NMR at low frequency bands

E. ANOARDO

Conferencia; 7th Conference on Field Cycling NMR relaxometry; 2011

Among others, prepolarization and field-cycling solutions were used to tackle the well known limitations related to signal to noise ratio at low fields. We can distinguish between three different situations: experiments at a low fixed field, experiments at “supposed” zero field and field-dependent experiments. Optimal hardware solutions for each case strongly depend on the involved relaxation times and the purpose of the experiment. The time dependence of the magnetic field during the switching, the damping time & peak values of transients and the NMR conditions for signal detection are also critical parameters. But, how critical are these parameters for field-cycling experiments? Which parameters are critical for relaxometry experiments within the ULF (ultra low frequency) band? What means doing NMR relaxometry within the ULF or lower frequency bands? Do local fields represent any limitation? How can local fields be quantified? Is this really a must? When is needed a magnetic field compensation? If field-cycling turns too complex, why not ULF experiments in the rotating frame or by multipulse sequences? The aim of the talk is to revise and trigger the discussion about these topics. Some advances will be commented on technical developments in progress related to the discussion.