Two-pulse Hahn echo pulse program for Bruker ASX spectrometer

Without the phase cycling proposed by E. Oldfield's group, the interpulse delay tau2 should be twice the duration of the central transition FID to observe the echoes. As a result, the echo amplitudes become small due to the spin-spin relaxation. Thank to this phase cycling, tau2 can be as short as the duration of the central transition FID.

Hahn echo sequence with this phase cycling also cancels the spurious signals such as the ringing generated by the nmr probe head or the signals from piezo electric materials in single crystal.

    ze
  1 d1 tlo           ; recycle duration d1
                     ; tlo set to drive HP X amplifier
    10u:c4
    p1:t:c4 ph1      ; the first-pulse duration p1
    d6:c4            ; spacing between pulses
    p2:t:c4 ph2      ; the second-pulse duration p2
    2u:c4
    d7 ph0:r         ; acquisition delay
    3u adc
    aq               ; acquisition
    1m
    rcyc=1  ph3      ; loop to 1, NS times for averaging
    wr #0
  exit

  ph0= 0
  ph1= (4) {0 0 0 0}^1^2^3     ; p1 pulse phase
  ph2= (4) {0 2 1 3}^1^2^3     ; p2 pulse phase
  ph3=     {0 0 2 2}^1^2^3     ; receiver phase