Multifrequency Pulsed EPR and the Characterization of Molecular Dynamics

Abstract

In fluid solution motion-dependent processes dominate electron spin lattice relaxation for nitroxides and semiquinones at frequencies between 250 MHz and 34 GHz. For triarylmethyl radicals motion-dependent processes dominate spin lattice relaxation at frequencies below about 3 GHz. The frequency dependence of relaxation provides invaluable information about dynamic processes occurring with characteristic times on the order of the electron Zeeman frequency. Relaxation mechanisms, methods of measuring spin-lattice relaxation, and motional processes for nitroxide, semiquinone, and triarylmethyl radicals are discussed.

Illuminating Ligand Field Contributions to Molecular Qubit Spin Relaxation via T1 Anisotropy

“…The T 1 anisotropy values are very similar between X-and Q-band and additionally between inversion recovery and saturation recovery (Table S2), validating T 1 anisotropy as an intrinsic molecular property rather than an artifact of spectral diffusion. 30 Owing to enhanced signal-to-noise, the X-band inversion recovery data (Figure 3) are most reliable and henceforth analyzed, additionally including the X-band CW saturation recovery value for Cu(dtc) 2 from ref 23.…”

Echo Trains in Pulsed Electron Spin Resonance of a Strongly Coupled Spin Ensemble

“…The presence of these multiecho signatures is explained using a simple model based on spins rotating on the Bloch sphere, backed up by numerical calculations using the inhomogeneous Tavis-Cummings Hamiltonian. DOI: 10.1103/PhysRevLett.125.137701 Pulsed electron spin resonance (ESR) is an essential spectroscopy technique used in many fields of science, e.g., for the study of the structure and dynamics of molecular systems [1,2], and for material science [3], as well as for quantum sensing and information applications [4][5][6]. To implement this technique, a vast repertoire of sophisticated pulse sequences exists [7], each of them optimized to investigate particular spin properties.…”

“…We determine the corresponding coupling rate g eff =2π ¼ 1.54 MHz from the vacuum Rabi splitting at B 0 ¼ 170. 19 mT, corresponding to a cooperativity C ¼ g 2 eff =ðκ c γ s Þ ¼ 12.2. Note that the single spinresonator coupling rate is not spatially uniform [25,59].…”

“…(a) Schematic of the Hahn echo sequence and the associated states in the Bloch sphere (exterior black arrows indicate the ensuing spin dynamics). A π=2 pulse is applied between (1) and(2) and an imperfect π pulse between (3) and (4), leading to the first (conventional) Hahn echo between(5) and(6). For the subsequent pulse train observed in the strong coupling limit, the spin packets indicated by blue and red arrows are crucial, which lie in opposite S y directions when the first π pulse arrives at (3) (see text).…”

Echo trains in pulsed electron spin resonance of a strongly coupled spin ensemble

“…Pulsed electron spin resonance (ESR) is an essential spectroscopy technique used in many fields of science, e.g. for the study of the structure and dynamics of molecular systems [1,2], material science [3] as well as quantum sensing and information applications [4][5][6]. For this technique, a vast repertoire of sophisticated pulse sequences exists [7], each of them optimized to investigate particular spin properties.…”