Eigenstate versus Zeeman‐based approaches to the solid effect. (15th April 2018)

• Record Type: Journal Article
• Authors: Rodríguez‐Arias, Inés; Rosso, Alberto; De Luca, Andrea
• Other Names: Dumez Jean‐Nicolas guestEditor.
• Is Part Of: Magnetic resonance in chemistry. Volume 56:Number 7(2018)
• Page Start: 689
• Page End: 698
• Publication Date: 2018-04-15
• Subjects: Nuclear magnetic resonance spectroscopy -- Periodicals; Chemistry, Organic -- Periodicals; Magnetic resonance -- Periodicals; 538.36
• DOI: 10.1002/mrc.4724
• Languages: English
• ISSNs: 0749-1581

Abstract

Abstract : The solid effect is one of the simplest and most effective mechanisms for dynamic nuclear polarization. It involves the exchange of polarization between one electron and one nuclear spin coupled via the hyperfine interaction. Even for such a small spin system, the theoretical understanding is complicated by the contact with the lattice and the microwave irradiation. Both being weak, they can be treated within perturbation theory. In this work, we analyze the two most popular perturbation schemes: the Zeeman and the eigenstate‐based approaches, which differ in the way the hyperfine interaction is treated. For both schemes, we derive from first principles an effective Liouville equation that describes the density matrix of the spin system; we then study numerically the behavior of the nuclear polarization for several values of the hyperfine coupling. In general, we obtain that the Zeeman‐based approach underestimates the value of the nuclear polarization. By performing a projection onto the diagonal part of the spin‐system density matrix, we are able to understand the origin of the discrepancy, which is due to the presence of parasite leakage transitions appearing whenever the Zeeman basis is employed. Abstract : In this paper, we study the solid effect, a dynamic nuclear polarization mechanism based on a two‐body resonance between one electron and one nuclear spin. In particular, we discuss the two most popular perturbation schemes used in dynamic nuclear polarization: the Zeeman and the interacting approaches. We show that for weak hyperfine interactions, the two schemes provide similar results, whereas for strong interactions, the Zeeman approach is no reliable.