Spectra of multiquantum echo signals from quadrupole nuclei with half-integral spin in magnetically ordered materials

The numerical simulation of two-pulse echo signals at times 2 tau, 4 tau, a nd 6 tau for the I = 5/2 spin and at time 2 tau, 4 tau, and 8 tau for the I = 7/2 spin (tau is the time interval between exciting pulses) is carried o ut. It is shown that a delay by 2 tau in the moment of formation of the ech o results in the disappearance of extreme quadrupole satellites in the NMR spectrum obtained by recording the frequency dependence of the echo amplitu de. The echoes at the maximum possible time of formation (2I + 1)tau are on ly observed at the frequency of the purely magnetic spectroscopic transitio n +/- 1/2 reversible arrow -/+ 1/2; no such echoes are observed at the quad rupole satellite frequencies. The computations are compared with the experi mental results obtained for the Mn-55 nuclei (spin I = 5/2) in the perovski te GdCu3Mn4O12 and the spinel Li0.5Fe2.5O4 : Mn. (C) 2000 MAIK "Nauka/ Inte rperiodica".