Analytic theory of finite pulse effects involving spin-1 nucleus in rotating solids

Abstract

newline Abstract newlineUnderstanding the response of nuclear spins subjected to oscillating and#64257;elds has remained an newlineactive pursuit in methodology development in NMR spectroscopy. While methods to study newlinethe dynamics of spin-1/2 nuclei exist, such studies involving quadrupolar spins (spins with newlineIgt1/2) have always been fraught with diand#64259;culty. In particular, the evolution of nuclear newlinespins subjected to radio-frequency (RF) pulses in periodically driven multi-level systems newlinehas remained a challenging problem owing to the domineering presence of the quadrupolar newlineinteractions. Although, development of analytic methods in static solids have enhanced newlineour basic understanding of the experiments, straightforward extensions to rotating solids newlineremain less trivial. In particular, a uniform analytic framework that explicates the interplay newlinebetween the sample spinning frequency, amplitude of the RF pulse and the quadrupolar newlinecoupling constant remains an open problem in rotating solids. Consequently, optimizations newlinebased on numerical methods have gained prominence in the development of NMR methods in newlinequadrupolar nuclei. While investigations based on numerical methods are easier to implement newlineand provide results, they do not necessarily aand#64256;ord insights into the physical phenomena newlineunder study. As an alternative, analytic methods based on Floquet theory are explored in newlinethe thesis for studying the excitation process in multilevel systems. Speciand#64257;cally, eand#64256;ective newlinetime-propagators derived from analytic methods are proposed to describe the eand#64256;ects of RF newlinepulses in rotating solids in three-level (S=1) systems. Through comparisons with simulations newlineemerging from exact numerical methods, the suitability and exactness of the analytic methods newlineis examined over wide-range of experimental parameters. Additionally, the interference eand#64256;ects newlineobserved in spin-1/2 nuclei coupled to quadrupolar spins (say S=1) are also discussed.