Vacancy in silicon: Hyperfine interactions from electron-nuclear double resonance measurements

1987 ◽  
Vol 35 (4) ◽  
pp. 1566-1581 ◽  
Author(s):  
M. Sprenger ◽  
S. H. Muller ◽  
E. G. Sieverts ◽  
C. A. J. Ammerlaan
Keyword(s):  
Hyperfine Interactions ◽  
Double Resonance ◽  
Electron Nuclear Double Resonance

Electron Nuclear Double Resonance (ENDOR) Investigations of Organic Doublet Radicals in the Nematic and Smectic Phase of Liquid Crystals

1980 ◽  
Vol 34 (3) ◽  
pp. 305-310 ◽  
Author(s):  
B. Kirste ◽  
H. Kurreck
Keyword(s):  
Liquid Crystals ◽  
Liquid Crystalline ◽  
Hyperfine Interactions ◽  
Double Resonance ◽  
Electron Nuclear Double Resonance ◽  
Smectic A ◽  
Smectic Phases ◽  
Anisotropic Hyperfine ◽  
Different Types ◽  
Nematic Phases

Different types of organic doublet radicals have been investigated in isotropic, nematic, and smectic phases of liquid crystals by performing electron nuclear double resonance (ENDOR), general TRIPLE and special TRIPLE experiments. For this purpose phenalenyls (perinaphthenyls), galvinoxyl, tetra- tert.-butylcarbazolyl, and bis(biphenylenyl)propenyl radicals have been chosen including some partially deuterated and 13C-labeled compounds. Anisotropic hyperfine interactions and deuterium quadrupole couplings could be determined. Smectic A phases have proved to be advantageous as compared to nematic phases in these studies. Detailed information about the orientation of the radicals within the liquid-crystalline solvent and about the conformations of the radicals could be obtained.

Magnetic Resonance of Oxygen-Related Defects in Silicon

1985 ◽  
Vol 59 ◽  
Author(s):  
J. Michel ◽  
J. R. Niklas ◽  
J.-M. Spaeth
Keyword(s):  
Effective Mass ◽  
Hyperfine Interactions ◽  
Double Resonance ◽  
Uniaxial Stress ◽  
Esr Spectra ◽  
Electron Nuclear Double Resonance ◽  
The Core ◽  
Spin Resonance ◽  
Unpaired Spin ◽  
First Time

ABSTRACTThe electron spin resonance (ESR) of a number of vacancy-oxygen complexes created in electron irradiated Si containing oxygen is briefly reviewed. In these centers the unpaired spin density is highly localised (50–70%) on two Si sites within the complex. The ESR spectra of several paramagnetic thermal donors (TD+) formed by annealing oxygen-rich Si at 450 °C for one to several hundred hours are reviewed as well as recent experiments under uniaxial stress from which for the ground state a 2 valley effective mass-like wavefunction was derived. Results of electron nuclear double resonance (ENDOR) experiments on the TD+ ESR line “NL8” are presented for the first time. They reveal that all TD's identified in IR-spectroscopy are superimposed in the NL8 ESR line and that upon growth of the TD the structure of the core and the symmetry of the TD's is not changed. The hyperfine interactions with up to 7 shells of Si nuclei of 5 TD+'s were determined. Their size and tensor orientations are consistent with the two-valley effective mass-like wavefunction. 4 TD's identified in ENDOR could be correlated with IR-bands from growth kinetics. Although the ENDOR experiments so far do not yet lead to a detailed TD model, the model possibilities are narrowed down considerably by these results. The core must consist of nuclei with very low magnetic abundancy. It is tentatively suggested, that the core contains an O2 molecule.

Electron–nuclear double resonance measurement of hyperfine interactions in Eu2+:CaWO4

1970 ◽  
Vol 48 (5) ◽  
pp. 562-573 ◽  
Author(s):  
H. Kiefte ◽  
J. S. M. Harvey
Keyword(s):  
Crystal Field ◽  
Quadrupole Interaction ◽  
Hyperfine Interactions ◽  
Double Resonance ◽  
Electron Nuclear Double Resonance ◽  
Nuclear Moments ◽  
G Factor ◽  
Resonance Measurement ◽  
Anisotropic Contribution ◽  
Made In

The hyperfine interactions in Eu2+ located substitutionally in CaWO4 have been accurately measured at a temperature of 4.2 °K by the method of electron–nuclear double resonance. These measurements were made in an attempt to determine the effects of the crystal field on the hyperfine interactions by comparison with results obtained for atomic Eu and Eu2+ in CaF2.The results have been fitted with a 12-parameter hyperfine Hamiltonian. Four of these parameters are used to represent an anisotropic quadrupole interaction and three to represent an anisotropic contribution of the form J3I. It is found that the spherically averaged quadrupole interaction is shifted by almost 20% from its value in CaF2. The nuclear g factor is also found to be shitted and anisotropic. These results are discussed in terms of a crystal-field induced shielding of the nuclear moments.

Solvent effects of cobalt(II) phthalocyanine in sulfuric acid: a continuous wave and pulse EPR study

2003 ◽  
Vol 07 (02) ◽  
pp. 89-96 ◽  
Author(s):  
Cinzia Finazzo ◽  
Sabine Van Doorslaer ◽  
Arthur Schweiger
Keyword(s):  
Sulfuric Acid ◽  
Continuous Wave ◽  
Hyperfine Interactions ◽  
Double Resonance ◽  
Resonance Spectroscopy ◽  
Electron Nuclear Double Resonance ◽  
Paramagnetic Resonance ◽  
Metal Phthalocyanines ◽  
The Matrix ◽  
Detailed Assessment

Products based on metal phthalocyanines are widely used in industry. In the processing of these materials it is essential to control the conditions of the matrix the metal phthalocyanines are embedded in. Using the example of cobalt(II) phthalocyanine in sulfuric acid we show that continuous wave and pulse electron paramagnetic resonance and electron nuclear double resonance spectroscopy provide excellent tools to monitor the influence of the matrix on paramagnetic phthalocyanines. The g values, the cobalt hyperfine values, and the hyperfine and nuclear quadrupole couplings of the isoindole nitrogens, as well as the hyperfine interactions of the surrounding protons allow for a detailed assessment of the electronic structure of cobalt(II) phthalocyanine in sulfuric acid. Subtle differences between the system under study and related Co ( II ) porphyrin and corrin systems could be traced.

Paramagnetic resonance and electron nuclear double resonance of substitutional hydrogen atoms in CaF 2

1967 ◽  
Vol 297 (1450) ◽  
pp. 376-396 ◽  
Keyword(s):  
Room Temperature ◽  
Endor Spectrum ◽  
Hyperfine Interactions ◽  
Double Resonance ◽  
Hydrogen Atoms ◽  
Electron Nuclear Double Resonance ◽  
Paramagnetic Resonance ◽  
Infrared Measurements ◽  
X Irradiation ◽  
Induced Defects

Recent infrared measurements have shown that hydrogen dissolves in CaF 2 as H - ions in fluorine sites (Elliott, Hayes, Jones, MacDonald & Sennett 1965). X-irradiation of CaF 2 : H crystals at room temperature produces paramagnetic hydrogen atoms in interstitial sites (Hall & Schumacher 1962). The present work shows that X-irradiation of CaF 2 : H crystals at 77°K produces hydrogen atoms in fluorine sites. These substitutional hydrogen atoms move into interstitial sites at 135°K giving rise to the e. p. r. spectrum observed by Hall & Schumacher in room temperature irradiated crystals. The present paper contains a detailed description of the e. p. r. and endor spectrum of the substitutional atoms in CaF 2 . It is found that the hyperfine interactions with second shell fluorines are smaller than with third and fourth shell fluorines and an explanation is suggested for this effect. Endor measurements of first shell fluorines show a resolved structure due to indirect fluorine-fluorine interactions. The endor measurements are of interest in connexion with the production and annealing mechanisms of the irradiation-induced defects.

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