Recoupling the non-secular part of nuclear spin-spin interaction in solids

TL;DR

This paper identifies conditions under which non-secular terms in the nuclear spin-spin interaction Hamiltonian can be recoupled in solids, enabling new manipulation techniques for nuclear spins and insights into relaxation phenomena.

Contribution

It introduces specific conditions linking magnetic and rf fields that preserve non-secular interactions, resulting in a tunable, unconventional spin-spin Hamiltonian.

Findings

Recoupling of non-secular interactions under certain field conditions

Tunable spin-spin Hamiltonian with novel properties

Potential for advanced nuclear spin manipulation

Abstract

NMR spin-spin relaxation in solids in strong magnetic fields is normally described only with the help of the secular part of the full spin-spin interaction Hamiltonian. This approximation is associated with the averaging of the spin-spin interaction over the fast motion of spins under the combined action of the static and the radio-frequency (rf) fields. Here we report a set of conditions when the averaging over the above fast motion preserves some of the non-secular terms entering the full interaction Hamiltonian. These conditions relate the value of the static magnetic field with the frequency and the amplitude of the rf field. When the above conditions are satisfied, the effective recoupled spin-spin interaction Hamiltonian has an unconventional form with tunable parameters. These tunable Hamiltonian offers interesting possibilities to manipulate nuclear spins in solids and can shed new light on the fundamental properties of the nuclear spin-spin relaxation phenomenon.