Hyperfine couplings electron paramagnetic resonance spectra

Deuterium quadrupole coupling constants can also be obtained from electron nuclear double resonance (ENDOR).19 30 An observation of the hyperfine structure caused by quadrupole coupling in the electron paramagnetic resonance (EPR) spectrum, as for many lanthanide complexes, has not been reported for deuterium. The determination of nuclear quadrupole coupling constants from Mossbauer spectroscopy is not applicable to the deuterium nucleus. 

The esr spectrum of the paramagnetic component coincident to the metal-metal axis was observed at 4 K through the coupling of a single-crystal dielectric resonator of K2Pt(CN)4Bro.3o(H20)3 with an electron spin resonance spectrometer. Preliminary results include a line at g w 2 with a complex hyperfine structure (208). An impurity center associated with the presence of a copper(II) complex of Z>4a symmetry has recently been detected by esr (466). 

A paramagnetic atom with Td symmetry should give only one resonance line, but when this atom has a nuclear spin, the electron and nuclear spins can couple by hyperfine interaction, and for a nuclear spin I, each electronic spin component splits into 21+1 components giving the same number of Am/ = 0 resonances. For instance, the ESR spectrum of tetrahedral interstitial Al I = 5/2) produced by electron irradiation of AZ-doped silicon is an isotropic sextuplet due to transitions between the six nuclear sublevels of each electronic-spin component ([54], and references therein). The electron spin of a centre can also interact with the nuclear spins of neighbouring atoms to give additional structures and this is clearly shown for 29 Si atoms (I = 1/2) in Fig. 4 of [54]. The ESR spectrum can thus also determine the atomic structure of the centre. This can also occur for non-cubic centres and the hyperfine structure is superimposed on the orientational structure. 

---