ENDOR resonance

ENDOR-induced EPR 4.2 EI-EPR ENDOR resonance frequency correction 2.4 Separation of overlapped EPR spectra and of different orientations in a powder... 

Disregarding incorrect matching of the ENDOR resonance condition, the line shape of the EI-EPR spectrum is only identical to that of the EPR spectrum if35 (a) the induced ENDOR transition belongs to an I = 1/2 nucleus, (b) only cross relaxation processes of the type (ms, m() <- (ms - 1, mi 1) occur, (c) no relaxation takes place between different mr-states within a given ms-manifold. 

The hfs and quadrupole tensors of one of the nitrogen ligands have been determined with ENDOR by Calvo et al.63). The 14N-ENDOR transition frequencies observed between 11 and 23 MHz were found to depend significantly on the nuclear quantum number mCu of the EPR observer line. These shifts are due to Cu-N crossterms (Sect. 3.2) and amount to more than 1 MHz for certain orientations of B0. ENDOR resonances of... 

ENDOR resonances in the 5-10 MHz region in azidohemin have been assigned to the axial nitrogen... 

A terminal water or hydroxyl ligand is another source of proton hyperfine couplings in metalloproteins. Characteristically, these protons can usually be exchanged in deuterated media (unlike the constitutive protons discussed above), allowing for complementary H ENDOR studies on the exchanged samples. For example, ENDOR resonances from exchangeable... 

We refer to a textbook dealing with ENDOR resonance spectroscopy of radicals in solution [15] for a review of measurements on radicals showing hyperfine structure... 

Fig. 2.10 ENDOR spectra from single crystals of 2-aminoethyl hydrogen sulfate X-irradiated at 295 K. The ENDOR resonances labelled 1, 2, 4, and 5 result from proton couplings. The four resonances labelled a-d result from hfc and nqc due to the N nucleus in the radical H3N" CH2CH0S03. The resonances labelled A and B are attributed to another radical. The figure is reproduced from [28] with permission from the American Chemical Society...

Figure 17. Tau-suppression effects in ESEEM spectra and their potential use in identifying and correlating peaks. In a semi-classical model, the procedure entails the locking of the temporal aspects of the pulse sequence, that is, the preparation-evolution-detection re-gionsfsee Ponti Schweiger, 1994) to the precession frequency of a specific ENDOR resonance. One thereby renders the ENDOR transition transparent to the echo modulation inter-ferogram.

Figure 2. ENDOR transitions (dashed arrows) in the energy level diagrams for an electron interacting with a nuclear spin I = Vi (left scheme) and with a nuclear spin I = l(right scheme) for a single orientation. The resulting ENDOR resonance lines and their associated spectral parameters are shown in the bottom part.

The hyperfine interaction. A, of an unpaired electron with nearby nuclei can be obtained by the electron-nuclear double resonance (ENDOR) technique. The ENDOR resonance condition is given by... 

The ENDOR resonance conditions on the radiofrequency v and the flux density B are... 

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