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Selective 1H excitation
(using selzg)
PRELIMINARY SET-UP
  • Record a conventional 1H spectrum. Note the o1 of the selected resonance.
    • PARAMETER SET
    a selective excitation with rpar SELZG1H all (the pulse program selzg
    MODIFY SPECIFIC PARAMETERS
    The most important parameters to modify are the shape, the duration and the corresponding power level of the selective pulse (p11). The shape must be created from the xShape tool (for instance, spnam1=gauss1024) and the power level (sp1) and the selective pulse duration (p11) must be calibrated as described in selective pulse calibration using selzg.

    o1 is set on-resonance of a well-isolated selected resonance.

    ACQUISITION
    (minimum, ns=4 and ds=2).
    PROCESSING
    PLOT
    OBSERVATIONS
    We can use other selective pulse lengths and power levels as a function of the required selectivity. Each 6 dB, the pulse duration is doubled and each 20 dB, the pulse duration is multiplied by 10. On the other hand, the duration of the corresponding selective 180º pulse is the double of the calculated selective 90º pulse at the same power level. The following table can be used as a reference:
     
     
     
    10 ms
    20 ms
    40 ms
    80 ms
    100 ms
    selective 90º
    61
    67
    73
    79
    81
    selective 180º
    55
    61
    67
    73
    75
    selective 270º
    52
    58
    64
    70
    72
     

    Once the calibration has been succesfully carried out, the parameter set can be stored with the wpar command in order to be used in the future (for instance, wpar selzg all).

    When applying selective 90 or 270 degree pulses in other sequences, there is need for phase difference calculation between power levels sp1 and pl1. This phase correction must be applied on the selective pulses.

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