Resonance double electron

ELDOR is tlie acronym for electron-electron double resonance. In an ELDOR experiment [28] one observes a rednction in the EPR signal intensity of one hyperfme transition that results from the saturation of another EPR transition within the spin system. ELDOR measurements are still relatively rare bnt the experiment is fimily established in the EPR repertoire. 

Hyde J S, Chien J C W and Freed J 1968 Electron-electron double resonance of free radicals In solution J. Chem. Phys. 48 4211-26... 

As discussed in Chapter 6, in systems with more than one unpaired electron the ESR spectrum contains features that involve electron-electron coupling parameters analogous to the nuclear hyperfine parameters. In those types of samples the advantages of double resonance are carried out by employing the use of two different microwave frequencies, one fixed and saturating, and one variable frequency that searches for transitions. This technique is known as ELDOR (electron-electron double resonance).38,40,41,44 It has been used much less than ENDOR and usually requires custom-built equipment. 

C. Elsasser, M. Brecht and R. Bittl, Pulsed electron-electron double resonance on multinuclear metal clusters Assignment of spin projection factors bsed on the dipolar interaction, J. Am. Chem. Soc., 2002, 124, 12606. 

Double-resonance spectroscopy involves the use of two different sources of radiation. In the context of EPR, these usually are a microwave and a radiowave or (less common) a microwave and another microwave. The two combinations were originally called ENDOR (electron nuclear double resonance) and ELDOR (electron electron double resonance), but the development of many variations on this theme has led to a wide spectrum of derived techniques and associated acronyms, such as ESEEM (electron spin echo envelope modulation), which is a pulsed variant of ENDOR, or DEER (double electron electron spin resonance), which is a pulsed variant of ELDOR. The basic principle involves the saturation (partially or wholly) of an EPR absorption and the subsequent transfer of spin energy to a different absorption by means of the second radiation, leading to the detection of the difference signal. The requirement of saturability implies operation at close to liquid helium, or even lower, temperatures, which, combined with long experimentation times, produces a... 

The new techniques of phosphorescence-microwave multiplet resonance spectroscopy with optical detection have been reviewed by El-Sayed and Kwiram Such exciting experiments as the optical detection on electron-nuclear double resonance (ENDOR) and of electron-electron double resonance (EEDOR) in zero magnetic field have been achieved, and it is certain that much detailed knowledge concerning the phosphorescent states will evolve from this field. 

Elba reaction org chem The formation of anthracene derivatives by dehydration and cycllzation of diaryl ketone compounds which have a methyl group or methylene group heating to an elevated temperature is usually required. elbs re.ak shan ( ELDOR See electron electron double resonance. ( el,dor or e el de o ar ( electrical calorimeter analy chem Device to measure heat evolved (from fusion or vaporization, for example) measured quantities of heat are added electrically to the sample, and the temperature rise is noted. a lek tra kal kal a rlm ad ar)... 

Gao et al. (2006) considered the data on an electron double resonance spectra of the cation-radical in conjunction with the results of calculation within the DFT. The authors established that the methyl group at the double bond of the cyclohexene ring is responsible for deprotonation of the P-carotene cation-radical. This route of proton elimination produces the most stable radical leaving the Jt-conjugation system to be intact. Deprotonation at the polyene methyl groups would... 

The ENDOR technique refers to electron-nuclear double resonance. This consists of the effect on a partially saturated ESR line of simultaneously irradiating the sample with a radiofrequency to induce nuclear resonance transitions of hyperfine coupled nuclei. It may enable one to obtain information about signs of coupling constants. ELDOR is the technique corresponding to electron-electron double resonance. Such techniques, coupled with TRIPLE resonance, have been utilized and well described in a discussion of pyridine and 4,4-bipyridyl radical anion ESR spectra measured in sodium/liquid ammonia (80JMR<41)17). 

Two traditions have evolved concerning the naming of pulsed electron-electron double resonance, calling these experiments either DEER (double electron-electron resonance) or PELDOR (pulsed electron-electron double resonance). In the ensuing discussion we use each author s preferred designation for their experiments. The absence of a dead-time in the four-pulse DEER experiment is an advantage relative to the three-pulse DEER experiment. When all of the pulses of the three-pulse DEER experiment are at the same frequency, it becomes the 2 +1 pulse sequence.13,14... 

Weber et al. have developed pulsed electron double resonance (PELDOR) at S-band, and used it to probe the dipolar and exchange interactions in the bis-nitroxides 13 - 16, where in the ester-bridged compounds the exchange interactions are diminished relative to the acetylene-bridged compounds, whilst maintaining a similar separation.10 They also demonstrate distance measurements by this technique. 

Mapping Global Folds of Oligonucleotides by Pulsed Electron-Electron Double Resonance... 

The understanding of structure-dynamics-function relationships in oligonucleotides or oligonucleotide/protein complexes calls for biophysical methods that can resolve the structure and dynamics of such systems on the critical nanometer length scale. A modern electron paramagnetic resonance (EPR) method called pulsed electron-electron double resonance (PELDOR or DEER) has been shown to reliably and precisely provide distances and distance distributions in the range of 1.5-8 nm. In addition, recent experiments proved that a PELDOR experiment also contains information on the orientation of labels,... 

Denysenkov, V. P., Prisner, T. F., Stubbe, J., and Bennati, M. (2006). High-field pulsed electron-electron double resonance spectroscopy to determine the orientation of the tyrosyl radicals in ribonucleotide reductase. Proc. Natl. Acad. Sci. USA 103, 13386-13390. 

Milov, A. D., Ponomarev, A. B., and Tsvetkov, Y. D. (1984). Electron—electron double resonance in electron spin echo Model biradical systems and the sensitized photolysis of decalin. Chem. Phys. Lett. 110, 67—72. 

In this review, we focus on solution-state DNP studies utilizing the Overhauser effect. Solid-state DNP is not included in this review,9,10 nor are experiments where the hyperpolarization is performed in the solid state before melting11,12 or dissolving8,13,14 the sample into solution. Chemically induced DNP (CIDNP)15-17 and the Overhauser effect of conduction electrons18,19 are also excluded, and the interested reader is referred to the cited papers for more information. The principles and prospects of proton-electron double resonance imaging (PEDRI) are briefly included, as a thorough coverage of this research area is out of the scope of this document. 

To reach this conclusion, Turke et al. investigated the experimental parameters that should affect the evaluation of DNP enhancement and found a condition where they believed complete saturation of the ESR line occurred with no sample heating for 15N,16D-4-oxo- TEMPO.71 From there, they measured actual enhancements of E = —170 at 0.35 T, yielding a coupling factor of p < 0.34 at 27 °C. This experimental DNP data more closely approaches the NMRD data in the accompanying paper by Ben-nati et al., where a coupling factor of p = 0.35 was determined at 25 °C, which corresponds to a maximum predicted DNP signal enhancement of Emax = 218.76 Electron-electron double resonance (ELDOR) experi-... 

Roberts JE, Hoffman BM, Rutter R et al (1981) Electron double resonance of horseradish peroxidase Compound I. Detection of the porphyrin 7i-cation radical. J Biol Chem 256 2118-2121... 

There are many other specialized methods electron-electron double resonance (ELDOR), TRIPLE, HYSCORE (hyperfine sublevel correlation spectroscopy, which is similar to 2D-EPR), electron spin-echo, and so on these methods are not discussed here. 

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