Nuclear Magnetic Resonance Saturation and Rotary Saturation in Solids

Abstract

Nuclear spin-lattice relaxation times of Al in pure Al and Cu6' in annealed pure Cu have been measured with a nuclear induction spectrometer, by the method of saturation, The experimental values of Ti are 4.1~0.8 milliseconds for A127 and 3.0~0.6. milliseconds for Cu", in reasonable agreement with theory. The dispersion mode of the nuclear resonance was also observed, and it was found that y' (the real part of the rf susceptibility) does not saturate at the same level as the absorption, x", but remains roughly constant out to a radio-frequency 6eld intensity of about 2 gauss. Both x' and p" become narrower and nearly Lorentzian in shape above saturation. When the dc magnetic Geld modulation is increased from 14 to 41 cps the phase of the dispersion signal lags behind the modulation, presumably because the modulation period is then comparable to Ti. Large dispersion signals above saturation have also been observed for the Na" resonance in NaC1. This behavior of the dispersion mode is in conQict with the predictions of Bloembergen, Purcell, and Pound and of the Bloch equations. The validity of these theories is reexamined , and it is concluded that although they are applicable to nuclear resonance in liquids and gases, and to solids at small rf intensities, they contain incorrect assumptions as applied to solids at high rf power levels. The theory of Bloembergen, Purcell, and Pound is based on an assumption equivalent to that of a spin temperature. It is '

Stimulus-induced Rotary Saturation (SIRS): A potential method for the detection of neuronal currents with MRI

“…(Redfield, 1955) Redfield analyzed rotary saturation in solids using B 1lock fields large compared to the local fields. They derived a steady state magnetization change in the detected spin locked magnetization M ρ compared to its initial value M 0 for the solid state which is given by:…”

“…Thus the neuronal currents induced by the stimulus create the rotary saturation effect. In analogy with the classic rotary saturation experiment of Redfield (1955), we refer to this potential method as Stimulus-Induced Rotary Saturation (SIRS).…”

Rotating Frame Analog of Spin-Locking and Spin–Lattice Relaxation in the Doubly Rotating Frame

“…The third LF pulse is the probe pulse by which the RASL magnetization, namely the magnetization along We also carried out an experiment of the RA of rotary saturation by introducing a weak sinusoidal amplitude modulation to the rf field during the spin-locking LF pulse. The amplitude modulation produces an oscillating magnetic field perpendicular to H 2 in the DRF analogous to the usual rotary saturation (5,6). We observed that the RASL magnetization decreases when the modulation frequency is equal to or near γ H 2 , where γ is the gyromagnetic ratio of the nuclei.…”

“…Equation [5] is also derived from Eq. [3] with θ=0, and therefore, shows that the relaxation rate T 1DR -1 measured under the condition in Eq.…”

“…[5] describes the experimental curve for T 1DR -1 in Fig.3, we derived an explicit expression of T 1DR -1 from Eq. [5] by a similar procedure to that of Albert et al, and plotted the temperature dependence using their values of E a , τ 0 , A and B (16). However, the agreement of the obtained theoretical curve (broken line in A remarkable difference between our values and theirs is in τ 0 for the Cation tumbling.…”