Full determination of chemical shift tensor in magnetically oriented microcrystals with modulated rotation and temporal tilt

Abstract

Complete characterization of ¹³C chemical shift tensor in magnetically oriented microcrystal suspension (MOMS) is demonstrated with an inhouse ¹H-¹³C double resonance probe capable of rotating microcrystals and of tilting the sample temporarily during the period of NMR signal acquisition. The ¹³C chemical shift tensor in three-dimensional MOMS of l-alanine is determined from ¹³C rotation patterns around a tilted axis. The present results prove that even for micrometer-sized microcrystals the chemical shift tensor can be fully determined like in the case of a single piece of bulky crystal but without elaborate sample mounting. Two-dimensional experiments correlating chemical shifts for different sample orientations are also demonstrated.