Cogwheel phase cycling in z-filter 3QMAS pulse program for spin 3/2
Contributor: Y. Millot

Below NMR pulse program describes the z-filter with cogwheel phase cycling for (1D and 2D) +3QMAS experiment applied to nuclei with 3/2 spin.

Fig. 1: Z-filter 3QMAS NMR pulse sequence and coherence transfer pathway.
The echo amplitude and the antiecho amplitude have the same sign.

This NMR pulse program is for Bruker Avance spectrometers.

A pure absorption 2D spectrum is obtained with the shearing transformation.

Code for Avance NMR spectrometers

; YM-3qzfil1_5-cog24p.av
; cog24(0,4,19,7) = cog24(23,3,18,6)
; receiver phase for cogwheel with standard values:
; ph31 = (360/24)*6*m = 90*m 
;
; I = 3/2 3QMAS pulse program
; 3-pulse experiment with zero quantum filter: 
; excitation(±3Q) - conversion(0Q) - tau - 90° selective - ACQ(-1Q) 
; 90° selective pulse should be determined first using Hahn-echo, 
; determination by single pulse excitation is also possible 
; Then optimise P2 and finally P1, 2 or more iterations for P1 and P2 
; may be needed.
; For processing shearing transformation may be requested,
; use AU program xfshear
;
;ns :  24*n
;d1 :  recycle delay
;p1 :  excitation pulse at pl11
;p2 :  conversion pulse at pl11
;p3 :  90 degree selective pulse at pl13
;pl1 :  = 120 db
;pl11 : power level for excitation and conversion pulses
;pl13 : power level for selective pulse
;d4 : = 20u, delay for z-filter 
;d0 : = 3u
;in0 : 1 rotor period for synchronised experiment
;td1 : number of t1-experiments
;FnMODE : States
;MC2 : States

  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,
  d4 pl13:f1          ; set low power in f1 channel,
  (p3 ph3):f1         ; low-power 90° pulse,
  go=1 ph31           ; signal acquisition,
                      ; loop to 1, ns times for averaging,
  d1 mc #0 to 1 F1PH(ip1, id0)
                      ; delay for disk I/O, store signal,
                      ; increase FID number,
                      ; delete memory data,
                      ; do not perform dummy scans
                      ; with next acquisition,
                      ; increment p1 pulse phase by 360°/12 
                      ; for States procedure,
                      ; increment time d0 by in0,
  exit                ; end of the pulse program

ph10=(24) 0  1  2  3  4  5  6  7  8  9
         10 11 12 13 14 15 16 17 18 19
         20 21 22 23
ph1=(12) ph10*23      ; excitation pulse phase
ph2=     ph10*3       ; conversion pulse phase
ph3=     ph10*18      ; 90° selective pulse phase
ph31=    ph10*6       ; receiver phase :(360/24)*6*m=90*m
  

This pulse program remains valid for the third pulse with strong amplitude for better excitation of off-resonance nuclei.