Electron spin–lattice relaxation of Ni2+

1969 ◽  
Vol 47 (16) ◽  
pp. 1753-1756 ◽  
Author(s):  
K. P. Lee ◽  
D. Walsh
Keyword(s):  
Electron Spin ◽  
Lattice Relaxation ◽  
Magnesium Nitrate ◽  
Spin Lattice Relaxation ◽  
Direct Process ◽  
Effective Spin ◽  
Strongly Coupled ◽  
Spin Lattice ◽  
Phonon Bottleneck ◽  
Spin Triplet

The electron spin–lattice relaxation rate by the direct process for Ni2+ in lanthanum magnesium nitrate is surprisingly fast (5 × 103 s−1 at 1.55 °K). Ni2+ is a non-Kramers ion, however, and consequently is strongly coupled to the lattice in most cases. The effective spin triplet and the absence of both hyperfine structure and phonon bottleneck are optimum requirements for a maser material.

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.

SEMICLASSICAL THEORY OF PHONON RADIATION PROCESSES

1966 ◽  
Vol 44 (8) ◽  
pp. 1699-1714 ◽  
Author(s):  
J. Van Kranendonk
Keyword(s):  
Time Derivative ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Multipole Moments ◽  
Spin Variable ◽  
Effective Spin ◽  
Spin Lattice ◽  
Radiation Theory ◽  
Order Of Magnitude ◽  
Radiation Processes

For the various forms of the spin-lattice coupling in paramagnetic salts of the iron group ions, derived in a previous paper, a semiclassical phonon radiation theory is developed. The phonon fields are analyzed in terms of phonon multipole fields, and the phonon multipole moments are expressed in terms of the effective spin variable. The phonon multipole fields are all monopole fields in the sense that the corresponding static fields fall off at large distances as R−2, but they are monopole, dipole, and quadrupole fields as far as the angular dependence is concerned. As a result, the rates of emission by the different phonon multipoles are all of the same order of magnitude. The equation of motion of a dressed spin is derived, and the phonon radiation damping is shown to depend on the third time derivative of the phonon multipole moments. As an application, the classical theory of the resulting spin-lattice relaxation is discussed briefly.

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