Theory of two-frequency excitation in14N NQR

Abstract

A simple and effective technique for calculating the transient signals in three-level spin systems irradiated at one and two frequencies is described. Al1 possible signals are presented and discussed. The application of the two-frequency excitation technique for the investigation of the inhomogeneity of the crystalline lattiee is suggested.

Two-frequency multiple-pulse sequences in nitrogen-14 NQR

“…This magnetization achieves a maximum when the rotations angle in the sequence gr s = 180 ~ and depends on the resonance offset zXo)rp. This dependence shows that the multiplepulse regime can be applied for the investigation of the tensor of inhomogeneous broadening, correlation of this broadening at different transitions and the local distribution of impurities [14,17]. The experimental verification of these theoretical results will be given in future papers.…”

Secondary signals in two-frequency nuclear quadrupole resonance on 14N nuclei with I=1

“…As was mentioned above the Eqs. (5)- (10) were obtained in the approximation of the long relaxation times which are larger comparing the observation time. However T 2 = 5.3 and 3.3 ms for the frequencies m + and m À , respectively, so relaxation effects became important for the higher observation windows and it should be a subject of further studies.…”

“…Later an interest of researchers concentrated on observation of the secondary echo on the third NQR frequency under the two-frequency irradiation [4,6], as well as on possibility to use two-frequency multipulse sequences [9,10]. In this respect it is worth to note that there is a number of the publications including NQR on 14 N nuclei, where the secondary echoes [3,7,[9][10][11][12] have been predicted. However, in many cases these signals have not observed experimentally due to some reasons.…”