Performance of frequency-modulated pulses in NQR

Abstract

This paper presents an analysis of the performance of frequency-modulated pulses and of pulses modulated simultaneously in amplitude and frequency in the pure nuclear quadrupolar resonance (NQR) spectroscopy of spin 3/2 nuclei. Computer simulations are given of the offset compensation efficiency of such pulses as applied to single crystals. Spin evolution equations were solved numerically. Experimental measurements, using FM pulses, of the 35 C1 NQR of sodium chlorate (NaC1O3 ) single crystal and of mercuric chloride (HgCl 2 ) powder are reported. The results suggest that frequency modulated pulses are alternative pulses to composite pulses in NQR.

The application of frequency swept pulses for the acquisition of nuclear quadrupole resonance spectra

“…Theoretical and experimental investigations have suggested that shaped pulses suitable for NMR experiments can be readily applied to NQR experiments [66]. For instance, frequency modulated (FM) pulses have previously been applied in NQR experiments by Schurrer and Pérez [67]; however, these FM pulses possess a non-uniform ''zipper"-like excitation profile limited to distinct offset frequencies. Spectral ranges greater than 500 kHz can routinely be uniformly excited with WURST pulses [64,65,68], with excitation breadth limited by a combination of the resonance frequency and probe bandwidth, suggesting that WURST echo and WURST-QCPMG sequences may find use in NQR experiments for a variety of quadrupolar nuclei.…”

A general numerical analysis of time-domain NQR experiments

“…The performance of frequency-modulated pulses have been calculated numerically for spin-3/2 nuclei, but not for higher order spins [22]. Here, we illustrate the principles and value of the theoretical approach outlined in Section 2 with a study of the transient NQR response of an I = 9/2 spin system to a shaped pulse.…”