Dynamic polarization of a nuclear zeeman subsystem within the framework of the EPR spin-temperature concept

2000 ◽  
Vol 67 (3) ◽  
pp. 564-568
Author(s):  
V. G. Dubovets ◽  
I. I. Ugolev
Keyword(s):  
Dynamic Polarization ◽  
Spin Temperature ◽  
Zeeman Subsystem ◽  
Temperature Concept

Systematische Untersuchungen der dynamischen Protonenpolarisation in organischen Kristallen mit eingebauten Radikalzentren

1969 ◽  
Vol 24 (10) ◽  
pp. 1532-1541
Author(s):  
K. Grude ◽  
W. Müller-Warmuth
Keyword(s):  
Magnetic Field ◽  
Enhancement Factor ◽  
Electronic Transitions ◽  
Dynamic Polarization ◽  
Spin Temperature ◽  
Field Range ◽  
Stable Free Radical ◽  
Organic Systems ◽  
High Proton ◽  
Paramagnetic Centres

Abstract In order to produce high proton polarizations, several organic hydrocarbons have been doped with stable free radical molecules. Through the "solid state effect" a part of the electronic polarization in a magnetic field has been transferred to the protons of these materials. For this purpose, the "forbidden electronic transitions" of the combined electron-proton system have been saturated at about 37 GHz. The enhancement factor of the dynamic proton polarization was measured by pulsed NMR at 56 MHz. In phenanthrene with about 4 w.% bis-diphenylen-phenylallyl (BPA) a maximum polarization of 10.5% has been obtained at 1.5 °K and 13 200 gauss. This value may be increased by extending the temperature and magnetic field range. Systematic investigations in numerous organic systems have been carried out and have particularly yielded data on the frequency dependence and on the saturation behaviour of the enhancement curves. - Spin temperature theories of dynamic polarization have been considered to explain the results and to find possibilities for improving the polarization. In particular, the exchange interaction of the radicals and the distinction between relaxing and polarizing paramagnetic centres had to be taken into account.

scholarly journals Spin temperature concept verified by optical magnetometry of nuclear spins

2018 ◽  
Vol 97 (4) ◽  
Author(s):  
M. Vladimirova ◽  
S. Cronenberger ◽  
D. Scalbert ◽  
I. I. Ryzhov ◽  
V. S. Zapasskii ◽  
...  
Keyword(s):  
Nuclear Spins ◽  
Spin Temperature ◽  
Optical Magnetometry ◽  
Temperature Concept

Dynamic Polarization in Single Crystals of CaF2 Containing H Atoms as Paramagnetic Impurities

1969 ◽  
Vol 24 (11) ◽  
pp. 1737-1745
Author(s):  
P. Zegers
Keyword(s):  
Single Crystals ◽  
Spin System ◽  
Nuclear Spin ◽  
Microwave Power ◽  
Modulation Frequency ◽  
Thermal Contact ◽  
Dynamic Polarization ◽  
Spin Temperature ◽  
Nuclear Spin System ◽  
Paramagnetic Centres

Formulae for dynamic polarization in solids having an inhomogeneous electron spin system and a nuclear spin system which can be described by one single spin temperature were derived. It was assumed that the spin temperature, in the rotating frame of those paramagnetic centres which fulfil ωe=ω+ωn or ωe = ω-ωn j can increase due to thermal contact with the nuclear spin- system brought about by high microwave power. Field fluctuations, at the positions of the para­magnetic centres, due to relaxation flipping of surrounding nuclei and paramagnetic centres were also taken into account. Formulae obtained for the enhancement and polarization time as a func­tion of microwave power and for the enhancement as a function of field modulation frequency and -amplitude agreed well with the experimental results in CaF2 single crystals containing H atoms.

EPR studies on fluorocarbon microspheres. Dynamic polarization of fluorine nuclei and adsorbed He3

1984 ◽  
Vol 45 (6) ◽  
pp. 1033-1038 ◽  
Author(s):  
M. Chapellier ◽  
L. Sniadower ◽  
G. Dreyfus ◽  
H. Alloul ◽  
J. Cowen
Keyword(s):  
Dynamic Polarization

Dynamical Nuclear Polarization

2018 ◽  
Author(s):  
M. M. Glazov
Keyword(s):  
Spin Polarization ◽  
Nuclear Spin ◽  
Nuclear Polarization ◽  
Magnetic Moments ◽  
Nonlinear Effects ◽  
Many Body ◽  
Nuclear Spin Polarization ◽  
Optical Resonances ◽  
Dynamical Nuclear Polarization ◽  
Temperature Concept

The transfer of nonequilibrium spin polarization between the electron and nuclear subsystems is studied in detail. Usually, a thermal orientation of nuclei in magnetic field is negligible due to their small magnetic moments, but if electron spins are optically oriented, efficient nuclear spin polarization can occur. The microscopic approach to the dynamical nuclear polarization effect based on the kinetic equation method, along with a phenomenological but very powerful description of dynamical nuclear polarization in terms of the nuclear spin temperature concept is given. In this way, one can account for the interaction between neighbouring nuclei without solving a complex many-body problem. The hyperfine interaction also induces the feedback of polarized nuclei on the electron spin system giving rise to a number of nonlinear effects: bistability of nuclear spin polarization and anomalous Hanle effect, dragging and locking of optical resonances in quantum dots. Theory is illustrated by experimental data on dynamical nuclear polarization.

scholarly journals Fundamental limitations of the mode temperature concept in strongly coupled systems

2020 ◽  
Vol 75 (8) ◽  
pp. 803-807
Author(s):  
Svend-Age Biehs ◽  
Achim Kittel ◽  
Philippe Ben-Abdallah
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Strong Coupling ◽  
Quantum Systems ◽  
Coupled Systems ◽  
Strong Coupling Limit ◽  
Strongly Coupled ◽  
Fundamental Limitations ◽  
Temperature Concept ◽  
Vacuum Gap

AbstractWe theoretically analyze heat exchange between two quantum systems in interaction with external thermostats. We show that in the strong coupling limit the widely used concept of mode temperatures loses its thermodynamic foundation and therefore cannot be employed to make a valid statement on cooling and heating in such systems; instead, the incorrectly applied concept may result in a severe misinterpretation of the underlying physics. We illustrate these general conclusions by discussing recent experimental results reported on the nanoscale heat transfer through quantum fluctuations between two nanomechanical membranes separated by a vacuum gap.

The Spin Temperature and 21 cm Brightness of the Intergalactic Medium in the Pre-Reionization era

2006 ◽  
Vol 637 (1) ◽  
pp. L1-L4 ◽  
Author(s):  
Michael Kuhlen ◽  
Piero Madau ◽  
Ryan Montgomery
Keyword(s):  
Intergalactic Medium ◽  
Spin Temperature
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