Consideration of the dipole-dipole reservoir in nonstationary double resonance

Abstract

Manifestations of the dipole-dipole reservoir (DDR) of electron spins in nonstationary NNDOR and ENDOR are investigated, taking as an example the electron-nuclear spin system Cr 3+ − 53Cr− 27 Al in ruby. It is demonstrated, that a consistent consideration of the hyperfine structure of the EPR spectrum of the Cr 3+ ions explains the behaviour of the NMR signal of the 27Al nuclei, observed experimentally during saturation of NMR of the 53Cr nuclei. The ENDOR signals are calculated with allowance for the shift of the DDR temperature, and it is pointed out that the absorption signal of ENDOR can change its sign depending on nuclear detuning.