Coherent multipulse sequences in nitrogen-14 NQR

Revealing dipolar coupling with NQR off-resonant pulsed spin locking

“…One way of compensating for this poor sensitivity is to apply not just a single radio-frequency (rf) excitation pulse, but a rapid series of such pulses in order to "lock" the signal in time. [1][2][3][4][5] The idea behind this pulsed spin locking is to continually refocus the decoherence caused by the various line broadening mechanisms. Pulsed spin locking was first applied to NQR by Marino and Klainer 6 in the form known as a "spinlocked spin-echo" (SLSE) sequence, following the initial successful application of this sequence to nuclear magnetic resonance (NMR).…”

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

“…Here Vp = tp'Qrn" The average Hamiltonian of inhomogeneous broadening for PAMS can be written as [4] Q~~zTi~ =A(-'Opq(SzPqCosl[f~s --S;qsin~-)COS~ -'Jrl (AO~qr-A(l]rp)(Sq~- (5) and it commutes with the density matrix from Eq. (4) if Vp = Vs/2, gr = ts~ m and t~ is the pulse duration in the sequence.…”

“…1. The simplest multiple-pulse sequence which satisfies this purpose is the phase-alternated multiple-pulse sequence (PAMS) [2][3][4] ~p-('t--~s-x-2z-gt~-'t'),, (1) where ~p~ = coit p is the rotation angle of the nuclear magnetization by the preparatory radio-frequency (rf) pulse, directed along the x-axes in the rotating reference frame, tp and co~ are its duration and intensity, respectively, ~ts• are the same for all the pulses in the sequence, where plus and minus denote 180 ~ phase shifts, and n is the cycle number. The particular case of this sequence is the pulsed spin-locking sequence (PSLS) ~;-(z-v 91 and its limiting case (n--co) is the strong off-resonance comb (SORC) [5,6].…”

“…The theoretical and experimental investigation of multiple-pulse sequences in I4N NQR [2][3][4]9] are summed up in ref. 10 and we will take the content of that paper as a guidance for our theoretical description of the two-frequency multiple-pulse technique.…”

A study of the spin–echo spin-locking effect in multi-pulse sequences in 14N nuclear quadrupole resonance

“…Therefore, the great interest of researchers in the SLSE effect reflected in numerous publications of both experimental and theoretical nature [1,[7][8][9][10][11][12][13][14][15][16][17][18], is justified.…”