Electron spin-echo envelope modulation at S-band. 2: Hyperfine and weak nuclear quadrupole interaction effects forI>1/2

The analysis of the nuclear modulation often observed in the electron spin-echo signals gives information on the structural arrangement around the paramagnetic center and on the interactions undergone by the spin system. Most applications to date have been carried out at X-band (≈9 GHz). However, to run experiments at different operating frequencies yields more accurate results and increases the number of experimental situations that can be investigated. Here we analyze the two- and three-pulse modulation patterns simulated at S-band (≈3 GHz) where the modulation is due to two different nuclei of experimental interest at different electron-nucleus distances, and comparison is done with the corresponding X-band patterns.²H (I=1) and⁷Li (I=3/2) nuclei are chosen due to their low quadrupole moment, so that comparison can be done between the effects due to weak nuclear quadrupole interaction at the two bands. It is shown that at short distances the complicated patterns due to hyperfine couplings are successfully interpreted by Fourier transform in the frequency domain, and that the use of S-band is really of some advantage with respect to X-band in detecting the presence of a weak nuclear quadrupole interaction.