Z-filter pulse program from Bruker for 3QMAS of half-integer spin quadrupole nuclei
Below NMR pulse program describes the z-filter approach for (1D and 2D) +3Q-MAS experiment applied to quadrupolar nuclei with half-integer spin.
Fig. 1: Z-filter 3QMAS NMR pulse sequence and coherence transfer pathway.
The echo amplitude and the antiecho amplitude have the
same sign.
The
phase cyling for 3 strong pulses is discussed.
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
; mq3qzqf ; 3Q MAS pulse program for half-integer spin nuclei ; 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 : 12*n ;d1 : recycle delay ;p1 : excitation pulse at pl11 ;p2 : conversion pulse at pl11 ;p3 : 90 degree selective pulse at pl21 ;pl1 : = 120 db ;pl11 : power level for excitation and conversion pulses ;pl21 : power level for 180 degree selective pulse, ca. pl11 + 30 db ;d4 : z-filter delay ;d0 : = 1u or longer ;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 pl21: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 for States procedure, ; increment time d0 by in0, exit ; end of the pulse program ph1=(12) 0 ; excitation pulse phase ph2=(6) 0 0 1 1 2 2 3 3 4 4 5 5 ; conversion pulse phase ph3= 0 2 ; 90° selective pulse phase ph0= 0 ph31= 0 2 2 0 ; receiver phase
If the third pulse must be a strong RF pulse for better excitation of off-resonance nuclei, the phase cyclings of ph1, ph2, ph3, and ph31 should be the following for spin I = 3/2. However, there is no harm in applying these phase cyclings concerning 3-strong pulse sequence even when the third pulse is a weak RF pulse.
; ns: 24*n ; pl21 = pl11 ph1=(12) 0 2 4 6 8 10 ; excitation pulse phase ph2= 0 ; conversion pulse phase ph3=(4) 0 0 0 0 0 0 1 1 1 1 1 1 2 2 2 2 2 2 3 3 3 3 3 3 ; 90° pulse phase ph0= 0 ph31= 0 2 0 2 0 2 1 3 1 3 1 3 2 0 2 0 2 0 3 1 3 1 3 1 ; receiver phase