Pulsed Magnetic Resonance

The density matrix is used to investigate the effects of radiofrequency pulses on spin systems. In the rotating frame, the r.f. Hamiltonian in angular frequency units is time-independent and has a form given by Eq. (2.28)., 

Suppose that the density matrix r(0 ) of a spin system just prior to the application of a 0a pulse corresponds to the equilibrium magnetization Mq. Then r(0 ) oc 7/3, where / is identical to z in this case. At the end of the r.f. pulse, a is given by Eq. (2.11), 

For components of spin angular momentum, e = 1. It is a simple matter to obtain Eq. (2.51) by noting that (j(0) obeys a simple differential equation, which may be derived as follows  

FIGURE 2.2. Positive rotation of a in an orthogonal coordinate system spanned by /a, //3, and 

the equilibrium magnetization Mq is rotated by 90° to lie along the X axis in the rotating frame as expected. 

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Tollner, E.W. and Hung, Y.C. 1992. Low resolution pulse magnetic resonance for measuring moisture in selected grains and kernels. J. Agric. Eng. Res. 53 195-208. 

Bloom, M., Morrison, C., Stemin, E. and Thewalt, J. (1992). Spin echoes and the dynamic properties of membranes. In D. M. S. Bagguley, ed. Pulsed Magnetic Resonance NMR, ESR, and Optics. Oxford University Press, London, p. 274. 

Pulsed magnetic resonance experiments are represented by parallel time lines of the applied pulses and the signal (Figure 50.4A). We will introduce this formalism here to explain the spin-echo and, in the next section, the spin-echo MRI pulse sequence. The first line is the time line of the applied B pulses, also refeiTed to as radioffequency, or RF pulses because they are applied at the Larmor frequency, which are typically in the radiofrequency range. 

Bagl D.M.S. Bagguley, ed.. Pulsed Magnetic Resonance NMR, ESR, and Optics, Clarendon Press, Oxford, 1992. 

M. L. Buess and G. L. Peterson, "Acoustic ringing effects in pulsed magnetic resonance probes," Rev. Sci. Instrum. 49, 1151-1155 (1978). 

Hoff, A.J. (ed ) Advanced EPR, AppUcations in Biology and Biochemistry, Amsterdam Elsevier, 1989. Platz, M.S. (ed.) Kinetics and Spectroscopy of Carbenes and Biradicals, New York Plenum, 1990. I Haya, YJ. (ed.) Spin Chemistry, Tokyo The Oji International Conference on Spin Chemistry, 1991. Bagguley, D.M.S. (ed.) Pulsed Magnetic Resonance NMR, ESR and Optics, a Recognition of E.L. Hahn, Oxford Oxford University Press, 1992. 

D, M, S. Bagguley Pulsed Magnetic Resonance. Oxford Univ. Press, Oxford 1992. 

Rinard GA, Quine RW, Eaton SS, Eaton GR, Froncisz W. 1994. Relative benefits of overcoupled resonators vs inherently low-Q resonators for pulsed magnetic resonance. J Magn Reson A108 71-81. 

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