Cogwheel phase cycling in I = 5/2, 3 pulses, 3QMAS phase-modulated shifted-echo pulse program.
Contribution of Y. Millot

Below NMR pulse program describes the phase-modulated shifted-echo for (1D and 2D) +3Q-MAS experiment applied to quadrupolar nuclei with half-integer spin I = 5/2.

Strong pulses allow a better excitation of off-resonance spins.

This NMR pulse program is for Bruker Avance spectrometers.

After the Fourier transform with respect to t2, a tau-dependent first-order phase correction is performed to remove the phase modulation due to the shift and a t1-dependent first-order phase correction to perform the shearing transformation.

Code for Avance NMR spectrometers

; cogwheelmp3qShiftE

; 3Q MAS pulse program for I = 5/2 nuclei

; cogwheel phase-modulated shifted-echo

; 3-pulse experiment with full echo acquisition:
; excitation(3Q) - conversion(1Q) - tau - 180° - acquisition(-1Q),
; uses cogwheel phase cycling with alternating phases of the first pulse 
; and that of the receiver
; cog51(-5, 0, 3; 21) === cog51(-26, -21, -18; 0) 
; === cog51(25, 30, 33; 0)
; alternating the phases of the second pulse and those of the third pulse do
; not change the sign of the echo signal

;NS :  51*n
;d1 :  recycle delay
;p1 :  excitation pulse at pl11
;p2 :  conversion pulse at pl11
;p4 :  180 degree pulse at pl21
;cnst31 : MAS spin rate
;pl1 :  = 120 db
;pl11 : power level
;pl21 : power level
;d6 :  to allow full echo to build up
;l1 :  number of rotor cycles for whole echo
;d0 :  = 3u or longer
;in0 : 1 rotor period for synchronised experiment
;td1 : number of t1-experiments
;FnMODE : QF
;MC2 : QF

"d6=((1s*l1)/cnst31)-(p2/2)-(p4/2)"
                      ; set the delay d6 according to l1 and cnst31 
                      ; values by the spectrometer automatically,

  ze                  ; clear memory, new data replace old data,
                      ; switch AD converter to replace mode,
                      ; perform DS before next acquisition,

1 d1                  ; recycle delay,
  10u pl11:f1         ; 10 microsecond delay,
                      ; set high power in f1 channel,
  (p1 ph1):f1         ; high-power excitation pulse,
  d0                  ; delay between pulses, t1 increment,
  (p2 ph2):f1         ; high-power conversion pulse,
  d6                  ; delay tau calculated automatically,
  (p4 pl21 ph3):f1    ; low-power 180° pulse,
  go=1 ph31           ; signal acquisition,
                      ; loop to 1, NS times for averaging,

2 d1                  ; recycle delay,
  10u pl11:f1         ; 10 microsecond delay,
                      ; set high power in f1 channel,
  (p1 ph4):f1         ; high-power excitation pulse,
  d0                  ; delay between pulses, t1 increment,
  (p2 ph2):f1         ; high-power conversion pulse,
  d6                  ; delay tau calculated automatically,
  (p4 pl21 ph3):f1    ; low-power 180° pulse,
  go=2 ph30           ; signal acquisition,
                      ; loop to 2, NS times for averaging,
  d1 mc #0 to 1 F1QF(id0)
                      ; delay for disk I/O, store signal,
                      ; increase FID number,
                      ; delete memory data,
                      ; do not perform dummy scans
                      ; with next acquisition,
                      ; increment time d0 by in0,
  exit                ; end of the pulse program

ph10=(51) 0  1  2  3  4  5  6  7  8  9 
         10 11 12 13 14 15 16 17 18 19
         20 21 22 23 24 25 26 27 28 29
         30 31 32 33 34 35 36 37 38 39
         40 41 42 43 44 45 46 47 48 49
         50           ; standard phase,
ph11 = 2              ; 180° phase for changing
                      ; the phase of 1st pulse

ph1 = ph10*25         ; excitation pulse phase,
ph4 = ph1 + ph11      ; opposite excitation pulse phase,

ph2 = ph10*30         ; conversion pulse phase,
ph3 = ph10*33         ; 180° pulse phase,

ph31 = 0              ; receiver phase,
ph30 = 2              ; opposite receiver phase