SORDOR pulses: expansion of the Böhlen-Bodenhausen scheme for low-power broadband magnetic resonance.

Abstract

A novel type of efficient broadband pulse, called second-order phase dispersion by optimised rotation (SORDOR), has recently been introduced. In contrast to adiabatic excitation, SORDOR-90 pulses provide effective transverse 90${}^{\circ }$ rotations throughout their bandwidth, with a quadratic offset dependence of the phase in the $x,y$ plane. Together with phase-matched SORDOR-180 pulses, this enables the Böhlen-Bodenhausen broadband refocusing approach for linearly frequency-swept pulses to be extended to any type of 90${}^{\circ }$/180${}^{\circ }$ pulse-delay sequence. Example pulse shapes are characterised in theory and experiment, and an example application is given with a ${}^{19}F$-PROJECT experiment for measuring relaxation times with reduced distortions due to $J$-coupling evolution.