14N NMR Echo in NH4ClO4after the Pulse Sequence (θ1)x–τ–(θ2)y–t

Abstract

We have derived a closed-form expression for the solid echo signal of quadrupolarI= 1 nuclei after the pulse sequence (θ1)x–τ–(θ2)y–tfor arbitrary values of the RF nutation frequency ω1= γB1and the quadrupolar frequency ωQ. In the case of single crystals both the true echo term of this expression and its induction-signal-like terms are important as shown by experiments on14N nuclei in NH4ClO4crystal. Conditions for obtaining the maximal echo in powder samples are presented. A very lowB1field together with long RF pulses may distort even the central part of the spectrum, resulting in strange looking apparent spectra.