Multiple quantum NMR of spin-carrying molecules in nanopores: high order corrections to the two-spin/two-quantum Hamiltonian

TL;DR

This study explores high-order corrections to the two-spin/two-quantum Hamiltonian in multiple-quantum NMR of molecules in nanopores, revealing how these corrections influence coherence intensity profiles.

Contribution

It introduces the analysis of second order Hamiltonian corrections in MQ NMR within nanopores, enabling investigation of large spin systems beyond previous limitations.

Findings

Coherence profiles depend on second order Hamiltonian corrections.

Profiles can change from exponential to logarithmic with corrections.

High symmetry allows studying systems with hundreds of spins.

Abstract

This paper is devoted to the multiple-quantum (MQ) NMR spectroscopy in nanopores filled by a gas of spin-carrying molecules (s=1/2) in a strong external magnetic field. It turned out that the high symmetry of the spin system in nanopores yields a possibility to overcome the problem of the exponential growth of the Hilbert space dimension with an increase in the number of spins and to investigate MQ NMR dynamics in systems consisting of several hundred spins. We investigate the dependence of the MQ coherence intensities on their order (the profile of the MQ coherence intensities) for a spin system governed by the standard MQ NMR Hamiltonian (the nonsecular two-quantum/two-spin Hamiltonian) together with the second order correction of the average Hamiltonian theory. It is shown that the profile depends on the value of this correction and varies from the exponential to the logarithmic one.