Magnetic electron spin-echo

Figure Bl.15.11. Fomiation of electron spin echoes. (A) Magnetization of spin packets i,j, /rand / during a two-pulse experiment (rotating frame representation). (B) The pulse sequence used to produce a stimulated echo. In addition to this echo, which appears at r after the third pulse, all possible pairs of the tluee pulses produce primary echoes. These occur at times 2x, 2(x+T) and (x+2T).

In electron-spin-echo-detected EPR spectroscopy, spectral infomiation may, in principle, be obtained from a Fourier transfomiation of the second half of the echo shape, since it represents the FID of the refocused magnetizations, however, now recorded with much reduced deadtime problems. For the inhomogeneously broadened EPR lines considered here, however, the FID and therefore also the spin echo, show little structure. For this reason, the amplitude of tire echo is used as the main source of infomiation in ESE experiments. Recording the intensity of the two-pulse or tliree-pulse echo amplitude as a function of the external magnetic field defines electron-spm-echo- (ESE-)... 

In electron spin echo relaxation studies, the two-pulse echo amplitude, as a fiinction of tire pulse separation time T, gives a measure of the phase memory relaxation time from which can be extracted if Jj-effects are taken into consideration. Problems may arise from spectral diflfrision due to incomplete excitation of the EPR spectrum. In this case some of the transverse magnetization may leak into adjacent parts of the spectrum that have not been excited by the MW pulses. Spectral diflfrision effects can be suppressed by using the Carr-Purcell-Meiboom-Gill pulse sequence, which is also well known in NMR. The experiment involves using a sequence of n-pulses separated by 2r and can be denoted as [7i/2-(x-7i-T-echo) J. A series of echoes separated by lx is generated and the decay in their amplitudes is characterized by Ty. ... 

Electron nuclear double resonance (ENDOR) and electron spin-echo envelope modulation (ESEEM) are two of a variety of pulsed EPR techniques that are used to study paramagnetic metal centers in metalloenzymes. The techniques are discussed in Chapter 4 of reference la and will not be discussed in any detail here. The techniques can define electron-nuclear hyperfine interactions too small to be resolved within the natural width of the EPR line. For instance, as a paramagnetic transition metal center in a metalloprotein interacts with magnetic nuclei such as H, H, P, or these... 

Dzuba, S.A. and Hoff, A.J. (2000) Photo-induced radical pairs investigated usin-out of phase electron-spin echo, In Berliner, L. J., Eaton, S. S., and Eaton, G. R. (eds.), (2000) Biological Magnetic Resonance, 19, Distance Measurements in biological Systems by EPR, Kluwer Academic/Plenum Publisher, N. Y., pp. 

Mims, W. B., Peisach, J. Electron Spin Echo Spectroscopy and the Study of Metalloproteins in Biological Magnetic Resonance, Vol. 3, (eds.) Berliner, L. J., Reuben, J., pp 213-263, New York, Plenum Press, 1981... 

CEMS = conversion electron Mossbauer spectroscopy DFT = density functional theory EFG = electric field gradient EPR = electron paramagnetic resonance ESEEM = electron spin echo envelope modulation spectroscopy GTO = Gaussian-type orbitals hTH = human tyrosine hydroxylase MIMOS = miniaturized mossbauer spectrometer NFS = nuclear forward scattering NMR = nuclear magnetic resonance RFQ = rapid freeze quench SAM = S -adenosyl-L-methionine SCC = self-consistent charge STOs = slater-type orbitals TMP = tetramesitylporphyrin XAS = X-ray absorption spectroscopy. 

EPR = Electron paramagnetic resonance EXAFS = Extended X-ray fine stmctnre analysis ESEEM = Electron spin echo envelope spectroscopy XANES = X-ray absorption near edge stmctnre analysis NMR = Nnclear magnetic resonance. 

Electron Paramagnetic Resonance (EPR) Spectroscopy, Electron Spin Echo Envelope Modulation (ESEEM) Spectroscopy Electron-Nuclear Double Resonance (ENDOR) Spectroscopy Nuclear Magnetic Resonance (NMR) Spectroscopy of Inorganic/Organometallic Molecules. 

In the last few years, pulsed EPR or electron spin echo (ESE) and reaction yield detected magnetic resonance (RYDMAR) techniques have been added to the arsenal of EPR techniques applied in photosynthesis. ESE combines high temporal resolution (currently 100 ns) with sensitivity to broad EPR signals, and it allows rapid and accurate determination of the spin-lattice and spin-spin relaxation times. 

Moll, H. P. (1994). Electron Paramagnetic Resonance in High Magnetic Field using Far Infrared Lasers Electron Spin Echoes at 604 GHz. Diplomarbeit, Universitat Konstanz. 

Long range dipolar interactions between an unpaired electron and nuclear spins on adjacent atoms will not normally be resolved in conventional powder EPR spectra.The pulse technique of electron spin echo modulation (ESEM) is in favourable cases able to detect very weak hyperfine interactions not seen in CW EPR. The method measures modulation of the electron spin echo signal by dipolar hyperfine coupling in the time domain at fixed magnetic field. Until recently,... 

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