EXPERIMENTAL ISSUES ON FIELD-CYCLING NMR: CRITICAL ASPECTS, PHYSICAL AND TECHNICAL LIMITS

E. ANOARDO

Otro; Ampere NMR School; 2019

We start with abrief revission of important historical aspects related to the evolution offield-cycling NMR: what was lost in the history? Fast-cycling of a magneticfield on diverse materials may turn far to be innocuous, specialy if low-field relaxationexperiments are considered [1]. Two kinds of limitations may affect afield-cycling NMR experiment [2]. Physical limitations that are intrinsicallyrelated to the sample (Type I): even if the perfect hardware would be available(whatever this means), the experiment will turn ill-defined due to intrinsic sampleproperties. Here the point is: how to detect this situation? False T1-dispersionsmay be misinterpreted in terms of unrealistic physical models. The second kind(Type II), even when also related to sample properties, may be manageable afterreaching an adequate hardware performance. However, this last possibility willfind a limit that is associated with the available technology and its relatedcosts, a matter that certainly evolves with time. Particular examples will beanalyzed.  References[1] R. Kimmich, Principle, Purpose and Pitfalls ofField-cycling NMR Relaxometry. In ?Field Cycling NMR Relaxometry?, R.Kimmich Editor, Royal Society of Chemistry, London (2019).[2] E. Anoardo, S.Kruber, G. O. Forte and G. A. Dominguez, New Trends in Fast-Field-CyclingNMR Technology. In ?Field Cycling NMR Relaxometry?, R. Kimmich Editor,Royal Society of Chemistry, London (2019).