Sideband separation experiments in NMR with phase incremented echo train acquisition

Abstract

A general approach for enhancing sensitivity of nuclear magnetic resonance sideband separation experiments, such as Two-Dimensional One Pulse (TOP), Magic-Angle Turning (MAT), and Phase Adjust Spinning Sidebands (PASS) experiments, with phase incremented echo-train acquisition (PIETA) is described. This approach is applicable whenever strong inhomogeneous broadenings dominate the unmodulated frequency resonances, such as in non-crystalline solids or in samples with large residual frequency anisotropy. PIETA provides significant sensitivity enhancements while also eliminating spectral artifacts would normally be present with Carr-Purcell-Meiboom-Gill acquisition. Additionally, an intuitive approach is presented for designing and processing echo train acquisition magnetic resonance experiments on rotating samples. Affine transformations are used to relate the two-dimensional signals acquired in TOP, MAT, and PASS experiments to a common coordinate system. Depending on sequence design and acquisition conditions two significant artifacts can arise from truncated acquisition time and discontinuous damping in the T2 decay. Here we show that the former artifact can always be eliminated through selection of a suitable affine transformation, and give the conditions in which the latter can be minimized or removed entirely.