Define the shape from the XWIN-NMR shape tool:

• Select HalfGauss from the Shapes menu and modify the following parameters if required:

Size of Shape: 1000
Truncation Level: 1

• Store the shape from the File-->Save As ... menu.
• Otherwhise, the shape can be generated directly from the XWIN-NMR command line:
Syntax:
st generate HalfGauss <size> <trunclevel>
or
st generate HalfGauss <size> false <trunclevel>

In the second case only amplitude data are generated.
int <size> = shape size in number of points
double <trunclevel> = truncation level in per cent

Example: st generate HalfGauss 1000 1

From the Analyze menu we can obtain the following information:

• Calculate Bandwith for Excitation [bandw2]

    Total rotation (in degree): 90
    DeltaOmega*DeltaT factor using transverse magn.: 1.88
• Calculate Bandwith for Inversion [bandw2i]

    Total rotation (in degree): 180
    DeltaOmega*DeltaT factor using -Mz: 0.628
• Calculate Bandwith for Refocusing -My [bandw2ry]

    Define Total rotation (in degree): 180
    DeltaOmega*DeltaT factor using -My: 0.462
• Calculate gammaB1max on Resonance [calcb1m]

    Length of pulse (in us): 10000
    Total rotation (in degree): 90
    Maximum gammaB1 (on resonance): 60.6689
    Corresponding 90 degree square pulse: 4120.73
• Calculate gammaB1max off Resonance [calcb1mo]

    Length of pulse (in us): 10000
    Total rotation (in degree): 90
   Offset (in Hz): 3000
    Maximum gammaB1 (off resonance): 4751.38
    Corresponding 90 degree square pulse: 52.6163
• Calculate average Power Level [calcpav]

    Amplitude relative to a square pulse of 100%: 0.412073
    Corresponding difference in dB: 7.70053
   Power relative to a square pulse of 100%: 0.169804
• Integrate Shape and compare to Square [integr]

    Integral ratio compared to a square pulse of 100%: 0.412073
    Corresponding difference in dB: -7.70053
• Integrate Shape compared to Hard Pulse [integr2]

    Length of pulse (in us): 10000
    Length of hard pulse (in us): 10
    Integral ratio compared to a square pulse of 100%: 0.412073
    Change of power level compared to level of hard pulse in dB: 52.2995

 
 

90 degree Half-Gaussian Shape   (in ms)	1	5	10	20	40	60	80	100
Maximum gammaB1   (on resonance) (in Hz)	606.7	121.3	60.7	30.3	15.2	10.1	7.6	6.1
Corresponding 90 degree  square pulse (in ms)	0.41	2.06	4.12	8.24	16.48	24.72	32.96	41.20
Change of power level   compared to level of a 10 us hard  90 degree pulse (in dB)	32.29	46.28	52.3	58.32	64.34	67.86	70.36	72.3

 
 

Amplitude relative to a   square pulse of 100%	0.412
Corresponding difference to a 100%   square pulse of the same duration (in dB)	7.7

 

 More sophisticated excitation schemes can be derived from the Manipulate menu.

The theoretical excitation profile of a half-gaussian shaped 90 degree pulse can be visualized from the NMRSIM program:

1. Select the corresponding File-->Experiment Setup-->Load from File ... menu.
2. Choose the profile.cfg configuration file.
3. Set the shape to hgauss3.shp in the Go-->Check Experiment parameters menu.
4. Select the Go-->Run Experiment menu.
5. The result of the simulation is displayed in the nmrsim 1 1 file into the XWIN-NMR window. Transform the data with ef (lb=1).

The duration of the shaped pulse can be modified by changing the P5 parameter (by default, 5 ms) in the Go-->Check Experiment parameters menu. Repeat the 4 and 5 steps to obtain the new profile.