Abstract
The effect of the applied RF field in an NMR experiment on the magnitude of the Spectral Density for a Dipolar Relaxation Mechanism is demonstrated theoretically. The effect is shown with Sin Cos Pulse as a concrete example. The order of magnitude of the magnetic moment where these effects will be significant for typical Rf amplitude values is derived. The effect may be of utility in providing an alternate method of control for MRI Tissue Contrast applications with further development.
Highlights
In contemporary NMR methodologies, it is common to find experimental scenarios where the relaxation of the magnetization during a pulse train is important to be able to model and quantify [1,2,3]
As can be seen there is found to be an appreciable dependence of the Spectral Density on the parameter Ku This is taken to indicate that the RF Field, with a range of values which will be discussed below, can affect the Spectral Density which is used to compute relaxation functions [6,13,14,15]
The reader may wonder what is a lower bound on the magnetic moment of the particle of Interest for a typical value of the pulse amplitude
Summary
In contemporary NMR methodologies, it is common to find experimental scenarios where the relaxation of the magnetization during a pulse train is important to be able to model and quantify [1,2,3]. During the course of working on this concept, it has come to our attention that the Russian investigator Sitnitsky [4] has investigated this phenomenon This proposed influence may be important in some models for explaining experimental data, such as for Liquid Crystals [5]. We note that the proposed effects may be useful as another avenue to control the spin dynamics of an experimental system while the pulse is on. We envision a spin system, transformed to the so called Tilted Doubly Rotating Frame (TDRF [8]). In this frame there will be defined a so-called “effective field.”. In the TDRF the effective field can be seen from geometric arguments to be defined as:.
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