High-field ENDOR

Proper single crystal-like ENDOR spectra can best be obtained by saturating the low-and high-field flanks of an EPR spectrum. At these field positions the resolution of the ENDOR spectrum is increased and distortions of the ENDOR lines are minimized78- 79). 

Fig. 47. Temperature dependence of the high field part of the two-dimensional proton ENDOR spectrum of V(bz)2 diluted into ferrocene. (From Ref. 78)...

D. Goldfarb, High-field ENDOR as a characterization tool for functional sites in microporous materials, Phys. Chem. Chem. Phys., 8 (2006) 2325-2343. 

Freed, J. H. and Mobeus, K. (1992) Magnetic resonance. High-field EPR-ENDOR. Israel J. Chem. 32, 475-481. 

While all contributions to the spin Hamiltonian so far involve the electron spin and cause first-order energy shifts or splittings in the EPR spectrum, there are also terms that involve only nuclear spins. Aside from their importance for the calculation of ENDOR spectra, these terms may influence the EPR spectrum significantly in situations where the high-field approximation breaks down and second-order effects become important. The first of these interactions is the coupling of the nuclear spin to the external magnetic field, called the... 

Arieli D, Delabie A, Vaughan DEW et al (2002) Isomorphous substitution of Mn(II) into aluminophosphate zeotypes a combined high-field ENDOR and DFT study. J Phys Chem B 106 7509-7519... 

Arieli D, Prisner TF, Hertel M et al (2004) Resolving Mn framework sites in large cage aluminophosphate zeotypes by high field EPR and ENDOR spectroscopy. Phys Chem Chem Phys 6 172-181... 

Epel B, Manikandan P, Kroneck PMH, Goldfarb D (2001) High-field ENDOR and the sign of the hyperfine coupling. Appl Magn Reson 21(3-4) 287-297... 

For organic aromatic radicals, the EPR spectra at X-band frequencies (9 GHz) are difficult to distinguish, all of them are in resonance approximately at the free electron g value (2.0023), which indicates that the angular momentum is strongly quenched for these molecules, and a typical line-width of 1-2 mT. They can be characterized by ENDOR spectroscopy but also very efficiently distinguished by their g-tensor anisotropy observable by means of high-field EPR spectroscopy. This is demonstrated (Fig. 4) for two radicals created transiently within the photocycle of photosynthetic purple bacteria... 

Co-ENDOR Co-ENDOR transitions in the frequency range 40 to 220 MHz have been detected using the high-field EPR line mcol = 5/2 as observer. The ENDOR spectrum consists of the four transition frequencies v(- 7/2 <- - 5/2 ms = 1/2) and v(- 5/2... 

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