An electron spin-lattice relaxation mechanism involving tunneling modes for trapped radicals in glassy matrixes. Theoretical development and application to trapped electrons in .gamma.-irradiated ethanol glasses

1977 ◽  
Vol 81 (5) ◽  
pp. 456-461 ◽  
Author(s):  
Michael K. Bowman ◽  
Larry Kevan
Keyword(s):  
Electron Spin ◽  
Lattice Relaxation ◽  
Relaxation Mechanism ◽  
Spin Lattice Relaxation ◽  
Theoretical Development ◽  
Trapped Electrons ◽  
Spin Lattice ◽  
Gamma Irradiated

Electron spin resonance studies of radicals condensed from irradiated water vapor: paramagnetic relaxation of trapped electrons in ice

1969 ◽  
Vol 47 (12) ◽  
pp. 2155-2160 ◽  
Author(s):  
P. Wardman ◽  
W. A. Seddon
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Trap Depth ◽  
Lattice Relaxation ◽  
Relaxation Mechanism ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Spin Resonance ◽  
Fast Passage

The spin–lattice relaxation time T1 of electrons (et−) trapped in several ice matrices at 77 °K has been estimated to be of the order of 10−2 s by observation of the electron spin resonance (e.s.r.) dispersion signal under fast passage conditions. These studies, together with measurements of the microwave power saturation of the e.s.r. absorption signal indicate that there is little difference in T1 at 77 °K for et− in solute-free polycrystalline H2O or D2O ice, γ-irradiated 8 M NaOH/H2O or NaOD/D2O glassy ices, and in 8 M NaOD/D2O glasses in which the electrons were produced by photoionization of ferrocyanide ion. This indicates that the predominant spin–lattice relaxation mechanism is not cross relaxation, and that correlations between T1 and line width or trap depth are inappropriate.

Pulse Shaped Dynamic Nuclear Polarization Under Magic Angle Spinning

2019 ◽  
Author(s):  
ASIF EQUBAL ◽  
Kan Tagami ◽  
Songi Han
Keyword(s):  
Electron Spin ◽  
Lattice Relaxation ◽  
Magic Angle Spinning ◽  
Spin Lattice Relaxation ◽  
Magic Angle ◽  
Total Electron ◽  
Spin Lattice ◽  
Maximum Benefit ◽  
Selective Saturation ◽  
Angle Spinning

In this paper, we report on an entirely novel way of improving the MAS-DNP efficiency by shaped μw pulse train irradiation for fast and broad-banded (FAB) saturation of the electron spin resonance. FAB-DNP achieved with Arbitrary Wave Generated shaped μw pulse trains facilitates effective and selective saturation of a defined fraction of the total electron spins, and provides superior control over the DNP efficiency under MAS. Experimental and quantum-mechanics based numerically simulated results together demonstrate that FAB-DNP significantly outperforms CW-DNP when the EPR-line of PAs is broadened by conformational distribution and exchange coupling. We demonstrate that the maximum benefit of FAB DNP is achieved when the electron spin-lattice relaxation is fast relative to the MAS frequency, i.e. at higher temperatures and/or when employing metals as PAs. Calculations predict that under short T<sub>1e </sub>conditions AWG-DNP can achieve as much as ~4-fold greater enhancement compared to CW-DNP.

A nuclear magnetic resonance investigation of solid tetraphosphorus trisulphide

1978 ◽  
Vol 364 (1719) ◽  
pp. 553-567 ◽  
Keyword(s):  
Phase 1 ◽  
Lattice Relaxation ◽  
Relaxation Mechanism ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Minor Role ◽  
High Resolution Spectrum ◽  
Basal Nuclei ◽  
Spin Lattice ◽  
A Minor

The 31 P n. m. r. spectrum and spin–lattice relaxation time in polycrystalline P 4 S 3 have been measured between 77 and 500 K in the range 7 to 25 MHz. In phase II the 31 P n. m. r. spectra and second moments are dominated by the anisotropic chemical shift interactions. Close to the first-order phase transition at 314 K the spectra are narrowed by reorientation of the molecules about their triad axes. This motion also generates anisotropicshift spin-lattice relaxation notable for its absence of frequency dependence. The activation energy of this motion was found to be 34 kJ mol -1 . Nuclear dipolar interactions play only a minor role. In phase 1 the molecules exhibit rapid quasi-isotropic reorientation and diffusion. The anisotropic broadening interactions are averaged out and an AB 3 high-resolution spectrum of a doublet and quartet are resolved at 420 K, well below the melting point, 446 K. In this phase the spin–rotation interaction relaxation mechanism becomes dominant. Taking advantage of the remarkable motional narrowing in this compound we report the first solid-state n. m. r. J spectrum. This spectrum, recorded at 410 K, allowed the J coupling between apical and basal nuclei in solid P 4 S 3 to be measured accurately, 70.4 ± 0.5 Hz.

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