Long-lived nuclear spin states far from magnetic equivalence

Abstract

Clusters of coupled nuclear spins may form long-lived nuclear spin states, which interact weakly with the environment, compared to ordinary nuclear magnetization. All experimental demonstrations of long-lived states have so far involved spin systems which are close to the condition of magnetic equivalence, in which the network of spin-spin couplings is conserved under pair exchanges of symmetryrelated nuclei. We show that the four-spin system of trans-[2,3-13C2]-but-2-enedioate exhibits a long-lived nuclear spin state, even though this spin system is very far from magnetic equivalence. The 4-spin long-lived state is accessed by slightly asymmetric chemical substitutions of the centrosymmetric molecular core. The long-lived state is a consequence of the locally centrosymmetric molecular geometry for the trans isomer, and is absent for the cis isomer. A general group theoretical description of long-lived states is presented. It is shown that the symmetries of coherent and incoherent interactions are both important for the existence of long-lived states.

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Identifiers

ORCID for Ilya Kuprov: orcid.org/0000-0003-0430-2682

ORCID for Lynda Jane Brown: orcid.org/0000-0002-5678-0814

ORCID for Richard Brown: orcid.org/0000-0003-0156-7087

ORCID for Giuseppe Pileio: orcid.org/0000-0001-9223-3896

ORCID for Malcolm H. Levitt: orcid.org/0000-0001-9878-1180

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