Zeeman Truncation in NMR. II. Time Averaging in the Rotating Frame
2015 (English)In: Concepts in magnetic resonance. Bridging education and research, ISSN 1546-6086, E-ISSN 1552-5023, Vol. 43, no 4, 109-126 p.Article in journal (Refereed) Published
The truncation of NMR interactions by the Zeeman Hamiltonian is here examined from a different perspective than that of our previous article [Concepts Magn. Reson., vol. 43A, pages 91-108 (2015)]: a Zeeman-truncated Hamiltonian is arranged by transforming the initially stationary operator of the NMR interaction into the rotating frame, followed by a time-averaging procedure over one Larmor period ( 2/0). We review the concept of an interaction frame, with focus on the rotating frame relevant for the Zeeman interaction, as well as the time-averaging procedure and the criteria for application of the resulting stationary Hamiltonian. A decisive advantage of this approach is its suitability for truncating time-dependent Hamiltonians, such as that of a radio-frequency (RF) field. Various options for reducing the time-dependent RF Hamiltonian into its stationary form are contrasted and thoroughly discussed. The role of Zeeman truncation is illustrated by examining the rotating-frame RF Hamiltonian associated with both on-resonance and off-resonance irradiation, where the time-independent operator character allows for applying the approximation strategies reviewed in our previous article.
Place, publisher, year, edition, pages
2015. Vol. 43, no 4, 109-126 p.
NMR Hamiltonians, RF Hamiltonian, interaction frame, time-averaging, average Hamiltonian theory
Chemical Sciences Physical Sciences Radiology, Nuclear Medicine and Medical Imaging
IdentifiersURN: urn:nbn:se:su:diva-117418DOI: 10.1002/cmr.a.21301ISI: 000353343600003OAI: oai:DiVA.org:su-117418DiVA: diva2:813908