Frequency shifts and relaxation rates for spin 1/2 particles moving in electromagnetic fields

TL;DR

This paper analyzes how non-uniform electromagnetic fields affect the Larmor frequency shift and relaxation rates of spin 1/2 particles, providing general relations applicable across various regimes and systems.

Contribution

It derives universal relations between frequency shifts and relaxation rates without assuming specific correlation functions, applicable to diverse particle motion regimes and geometries.

Findings

Derived general relations valid for diffusive and ballistic regimes

Results are independent of specific correlation function forms

Applicable to arbitrary cell shapes and surface scattering conditions

Abstract

We discuss the behaviour of the Larmor frequency shift and the longitudinal relaxation rate due to non-uniform electromagnetic fields on an assembly of spin 1/2 particles, in adiabatic and nonadiabatic regimes. We also show some general relations between the various frequency shifts and between the frequency shifts and relaxation rates. The remarkable feature of all our results is that they were obtained without any specific assumptions on the explicit form of the correlation functions of the fields. Hence, we expect that our results are valid both for diffusive and ballistic regime of motion and arbitrary cell shapes and surface scattering. These results can then be applied to a wide variety of realistic systems.