Multiple pulse response in pure NQR of spin I = 3/2 nuclei in single crystals: response to phase-alternated pulse sequence (PAPS)

Abstract

The response of spin I = 3/2 nuclei in a single crystal to phase-alternated pulse sequence (PAPS) t°_wl -(τ-t^180°_w2-2τ-t^0°_w2-τ)_N in pure NQR is theoretically investigated. Average Hamiltonian theory is employed to calculate the spin-space averaging of the line-broadening internal interactions. is employed to calculate the spin-space averaging of the line-broadening internal interactions. The criterion employed for spin-space averaging is that the average Hamiltonian during the cycle for the interaction under consideration should commute with the initial density matrix prepared by the pulse t^0°_w1 before the first cycle. The average Hamiltonian during PAPS for the main line-broadening interactions, namely electric field gradient (efg) inhomogeneity, torsional oscillations and heteronuclear dipolar interactions, is found to commute with the initial density matrix of the system when 2t_w1 = t_w2. It is concluded that during PAPS these internal interactions do not contribute to the linewidth of the pure NQR spectrum of physically equivalent spin I = 3/2 nuclei in a single crystal. These theoretical results are similar to those obtained earlier for spin I = 1 system by Osokin.