Solomon Echoes Extended to Soft Pulse Excitation

Abstract

Solomon echoes, produced by two in-phase pulses separated by a delay τ2, are derived in taking into account the first-order quadrupolar interaction during the pulses. Consequently, the results are valid for any ratio of the quadrupolar coupling, ωQ, to the amplitude of the radiofrequency pulse, ωRF. Six echoes are predicted after the second pulse: three, detected as inner satellite signals, occur at τ4= τ2, τ4= 2 τ2 and τ4= 3 τ2; the other three, detected as outer satellite signals, occur at τ4= τ2/2, τ4= τ2, and τ4 = 3 τ2/2. These echoes originate from the refocusing of single and multi-quantum off-resonance coherences developed during the first pulse. Four of them are allowed echoes, the other two are forbidden ones. However, there is no echo for the central transition. From a practical point of view this means that τ2 must be short compared to TFID, the duration of the FID of the central transition. The behavior of the echo amplitude versus the second pulse length is discussed for several ratios of ωQ/ωRF. © 1994, Verlag der Zeitschrift für Naturforschung. All rights reserved.