scholarly journals The decay of the refocused Hahn echo in DEER experiments

2021 ◽  
Author(s):  
Thorsten Bahrenberg ◽  
Samuel M. Jahn ◽  
Akiva Feintuch ◽  
Stefan Stoll ◽  
Daniella Goldfarb
Keyword(s):  
Electron Spin ◽  
Large Scale ◽  
Pulse Sequence ◽  
Spin Dynamics ◽  
Spin Echo ◽  
Sequence Length ◽  
Paramagnetic Resonance ◽  
Flip Flop ◽  
Spin Dephasing ◽  
Dynamics Simulations

Abstract. Double electron–electron resonance (DEER) is a pulse electron paramagnetic resonance (EPR) technique that measures distances between paramagnetic centres. It utilizes a four-pulse sequence based on the refocused Hahn spin echo. The echo decays with increasing pulse sequence length 2(τ1 + τ2), where τ1 and τ2 are the two time delays. In DEER, the value of τ2 is determined by the longest inter-spin distance that needs to be resolved, and τ1 is adjusted to maximize the echo amplitude and thus sensitivity. We show experimentally that for typical spin centres (nitroxyl, trityl, Gd(III)) diluted in frozen protonated solvents, the largest refocused echo amplitude for a given τ2 is obtained neither at very short τ1 (which minimizes the pulse sequence length) nor at τ1 = τ2 (which maximizes dynamic decoupling for a given total sequence length), but rather at τ1 values smaller than τ2. Large-scale spin dynamics simulations including the electron spin and several hundred neighbouring protons reproduce the experimentally observed behaviour almost quantitatively. They show that electron spin dephasing is driven by solvent protons via the flip-flop coupling among themselves and their hyperfine couplings to the electron spin.

scholarly journals The decay of the refocused Hahn echo in double electron–electron resonance (DEER) experiments

2021 ◽  
Vol 2 (1) ◽  
pp. 161-173
Author(s):  
Thorsten Bahrenberg ◽  
Samuel M. Jahn ◽  
Akiva Feintuch ◽  
Stefan Stoll ◽  
Daniella Goldfarb
Keyword(s):  
Electron Spin ◽  
Large Scale ◽  
Pulse Sequence ◽  
Spin Dynamics ◽  
Spin Echo ◽  
Sequence Length ◽  
Flip Flop ◽  
Electron Resonance ◽  
Double Electron ◽  
Double Electron Electron Resonance

Abstract. Double electron–electron resonance (DEER) is a pulse electron paramagnetic resonance (EPR) technique that measures distances between paramagnetic centres. It utilizes a four-pulse sequence based on the refocused Hahn spin echo. The echo decays with increasing pulse sequence length 2(τ1+τ2), where τ1 and τ2 are the two time delays. In DEER, the value of τ2 is determined by the longest inter-spin distance that needs to be resolved, and τ1 is adjusted to maximize the echo amplitude and, thus, sensitivity. We show experimentally that, for typical spin centres (nitroxyl, trityl, and Gd(III)) diluted in frozen protonated solvents, the largest refocused echo amplitude for a given τ2 is obtained neither at very short τ1 (which minimizes the pulse sequence length) nor at τ1=τ2 (which maximizes dynamic decoupling for a given total sequence length) but rather at τ1 values smaller than τ2. Large-scale spin dynamics simulations based on the coupled cluster expansion (CCE), including the electron spin and several hundred neighbouring protons, reproduce the experimentally observed behaviour almost quantitatively. They show that electron spin dephasing is driven by solvent protons via the flip-flop coupling among themselves and their hyperfine couplings to the electron spin.

Effect of electron spin dynamics on solid-state dynamic nuclear polarization performance

2014 ◽  
Vol 16 (35) ◽  
pp. 18694-18706 ◽  
Author(s):  
Ting Ann Siaw ◽  
Matthias Fehr ◽  
Alicia Lund ◽  
Allegra Latimer ◽  
Shamon A. Walker ◽  
...  
Keyword(s):  
Solid State ◽  
Electron Spin ◽  
Dynamic Nuclear Polarization ◽  
Nuclear Polarization ◽  
Spin Dynamics ◽  
Nitroxide Radicals ◽  
Flip Flop ◽  
State Dynamic ◽  
Spin Flip ◽  
Electron Spin Dynamics

Optimum integral EPR saturation, determined by electron T1e and electron spin flip-flop rate, maximizes solid-state DNP performance using nitroxide radicals.

scholarly journals Spin dynamics of light-induced charge separation in composites of semiconducting polymers and PC60BM revealed using Q-band pulse EPR

2017 ◽  
Vol 19 (33) ◽  
pp. 22141-22152 ◽  
Author(s):  
E. A. Lukina ◽  
E. Suturina ◽  
E. Reijerse ◽  
W. Lubitz ◽  
L. V. Kulik
Keyword(s):  
Electron Spin ◽  
Charge Separation ◽  
Spin Dynamics ◽  
Spin Echo ◽  
Electron Spin Echo ◽  
Semiconducting Polymers ◽  
Band Electron ◽  
Different Types ◽  
Pulse Epr ◽  
Induced Charge

Q-Band electron spin echo spectroscopy allows distinguishing light-induced polarons of different types in photovoltaic polymer/fullerene composites.

scholarly journals Triarylmethyl Radical: EPR Signal to Noise at Frequencies between 250 MHz and 1.5 GHz and Dependence of Relaxation on Radical and Salt Concentration and on Frequency

2017 ◽  
Vol 231 (4) ◽  
Author(s):  
Yilin Shi ◽  
Richard W. Quine ◽  
George A. Rinard ◽  
Laura Buchanan ◽  
Sandra S. Eaton ◽  
...  
Keyword(s):  
Spin Relaxation ◽  
Electron Spin ◽  
Salt Concentration ◽  
Spin Echo ◽  
Electron Spin Echo ◽  
Relaxation Rates ◽  
Optimum Frequency ◽  
Paramagnetic Resonance ◽  
Electron Spin Relaxation

AbstractIn vivo oximetry by pulsed electron paramagnetic resonance is based on measurements of changes in electron spin relaxation rates of probe molecules, such as the triarylmethyl radicals. A series of experiments was performed at frequencies between 250 MHz and 1.5 GHz to assist in the selection of an optimum frequency for oximetry. Electron spin relaxation rates for the triarylmethyl radical OX063 as a function of radical concentration, salt concentration, and resonance frequency were measured by electron spin echo 2-pulse decay and 3-pulse inversion recovery in the frequency range of 250 MHz–1.5 GHz. At constant OX063 concentration, 1/T

scholarly journals Walker-like domain wall breakdown in layered antiferromagnets driven by staggered spin–orbit fields

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Rubén M. Otxoa ◽  
P. E. Roy ◽  
R. Rama-Eiroa ◽  
J. Godinho ◽  
K. Y. Guslienko ◽  
...  
Keyword(s):  
Domain Wall ◽  
Large Scale ◽  
Domain Walls ◽  
Spin Dynamics ◽  
Continuum Theory ◽  
Dynamical Regime ◽  
Spin Orbit ◽  
Translational Invariance ◽  
Domain Structures ◽  
Dynamics Simulations

Abstract Within linear continuum theory, no magnetic texture can propagate faster than the maximum group velocity of the spin waves. Here, by atomistic spin dynamics simulations and supported by analytical theory, we report that a strongly non-linear transient regime due to the appearance of additional magnetic textures results in the breaking of the Lorentz translational invariance. This dynamical regime is akin to domain wall Walker-breakdown in ferromagnets and involves the nucleation of an antiferromagnetic domain wall pair. While one of the nucleated domain walls is accelerated beyond the magnonic limit, the remaining pair remains static. Under large spin–orbit fields, a cascade of multiple generation and recombination of domain walls are obtained. This result may clarify recent experiments on current pulse induced shattering of large domain structures into small fragmented domains and the subsequent slow recreation of large-scale domains.

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