Multi-spin dynamics of the solid-state NMR Free Induction Decay

TL;DR

This paper experimentally investigates the growth of multi-spin correlations during the free induction decay in solid-state NMR, revealing how spin geometry influences coherence development.

Contribution

It provides the first direct measurement of multi-spin coherence growth during FID in solid-state NMR, highlighting the role of lattice geometry.

Findings

Growth of multi-spin coherences observed during FID

Spin geometry significantly affects correlation development

Experimental results align with theoretical models

Abstract

We present a new experimental investigation of the NMR free induction decay (FID) in a lattice of spin-1/2 nuclei in a strong Zeeman field. Following a pi/2 pulse, evolution under the secular dipolar Hamiltonian preserves coherence number in the Zeeman eigenbasis, but changes the number of correlated spins in the state. The observed signal is seen to decay as single-spin, single-quantum coherences evolve into multiple-spin coherences under the action of the dipolar Hamiltonian. In order to probe the multiple-spin dynamics during the FID, we measured the growth of coherence orders in a basis other than the usual Zeeman eigenbasis. This measurement provides the first direct experimental observation of the growth of coherent multiple-spin correlations during the FID. Experiments were performed with a cubic lattice of spins (19F in calcium fluoride) and a linear spin chain (19F in fluorapatite). It is seen that the geometrical arrangement of the spins plays a significant role in the development of higher order correlations. The results are discussed in light of existing theoretical models.