Abstract : The theoretical shapes of nuclear spin-noise spectra in NMR are derived by considering a receiver circuit with finite, preamplifier input impedance and a transmission line between the preamplifier and the probe. Using this model, it becomes possible to reproduce all observed experimental features: variation of the NMR resonance linewidth as a function of the transmission line phase, nuclear spin-noise signals appearing as a ``bump'' or as a ``dip'' superimposed on the average electronic noise level even for a spin system and probe at the same temperature, pure in-phase Lorentzian spin-noise signals exhibiting non-vanishing frequency shifts. Extensive comparison to experimental measurements validate the model predictions, and define the conditions for obtaining pure in-phase Lorentzian-shape nuclear spin noise with a vanishing frequency shift, in other words, the conditions for simultaneously obtaining the Spin-Noise and Frequency-Shift Tuning Optima.
https://hal-cea.archives-ouvertes.fr/cea-01171610
Contributor : Herve Desvaux
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Submitted on : Friday, August 21, 2015 - 5:16:28 PM
Last modification on : Wednesday, January 23, 2019 - 2:38:32 PM
Long-term archiving on: Wednesday, April 26, 2017 - 10:06:51 AM
