Motion of free spins and NMR imaging without a radio-frequency magnetic field

TL;DR

This paper provides a quantum mechanical explanation for NMR imaging without radio-frequency magnetic fields, detailing how free spins produce detectable signals and phase shifts, potentially informing new MRI techniques and quantum computing applications.

Contribution

It offers a quantum theoretical framework for understanding free spin motion and NMR imaging without RF fields, expanding the fundamental understanding of magnetic resonance phenomena.

Findings

Explains phase shift in spin noise spectrum.

Accounts for high signal-to-noise ratio without RF pulses.

Provides a basis for new MRI sequences and quantum computing methods.

Abstract

NMR imaging without any radio-frequency magnetic field is explained by a quantum treatment of independent spin~$\tfrac 12$. The total magnetization is determined by means of their individual wave function. The theoretical treatment, based on fundamental axioms of quantum mechanics and solving explicitly the Schr\"{o}dinger equation with the kinetic energy part which gives the motion of free spins, is recalled. It explains the phase shift of the spin noise spectrum with its amplitude compared to the conventional NMR spectrum. Moreover it explains also the relatively good signal to noise ratio of NMR images obtained without a RF pulse. This derivation should be helpful for new magnetic resonance imaging sequences or for developing quantum computing by NMR.