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

Abstract

The theoretical investigation of the multiple-pulse sequences in which the radio-frequency pulses are applied simultaneously at two transitions are presented. The time-independent solution of the quantum Liouville equation for the average Hamiltonian of inhomogeneous broadening in the sequence is obtained by the projection operator technique. This solution predicts the multiple echo signals on the third transition that is not irradiated by radio-frequency pulses.

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

“…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.…”

Two-frequency composite pulses in NQR

“…The experimental results of reŸ 5 in accordance with this theory represent the echo signals at both irradiated transitions. This splitting of coherency arises also in the multiple-pulse regime [6]. Of course it is desirable to use the two-frequency irradiation in the multiplepulse regime.…”

“…Of course it is desirable to use the two-frequency irradiation in the multiplepulse regime. The calculation [6] shows that the separation of coherences takes place in this case also. So we will try to find the combination of two-frequency pulses that would be equivalent to a pulse at the third transition~ We will show that such pulse sequence can be constructed by the two-frequency irradiation in the way adopted for the formation of composite pulses.…”