Evidence of spin-temperature in dynamic nuclear polarization: an exact computation of the EPR spectrum. Issue 36 (5th September 2016)

• Record Type: Journal Article
• Authors: Caracciolo, Filippo; Filibian, Marta; Carretta, Pietro; Rosso, Alberto; De Luca, Andrea
• Is Part Of: Physical chemistry chemical physics. Volume 18:Issue 36(2016)
• Page Start: 25655
• Page End: 25662
• Publication Date: 2016-09-05
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c6cp05047f
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : We show the validity of the spin-temperature approach for typical radical concentration used in dissolution DNP protocols. Abstract : In dynamic nuclear polarization (DNP) experiments, the compound is driven out-of-equilibrium by the microwave (MW) irradiation of the radical electron spins. Their stationary state has been recently probed via electron double resonance (ELDOR) techniques showing, at low temperature, a broad depolarization of the electron paramagnetic resonance (EPR) spectrum under microwave irradiation. In this theoretical manuscript, we develop a numerical method to compute exactly the EPR spectrum in the presence of dipolar interactions. Our results reproduce the observed broad depolarisation and provide a microscopic justification for the spectral diffusion mechanism. We show the validity of the spin-temperature approach for typical radical concentration used in dissolution DNP protocols. In particular once the interactions are properly taken into account, the spin-temperature is consistent with the non-monotonic behavior of the EPR spectrum with a wide minimum around the irradiated frequency.