Define the shape from the XWIN-NMR shape tool:

• Select Gauss 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 Gauss <size> <trunclevel>
or
st generate Gauss <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 Gauss 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.: 2.122
• Calculate Bandwith for Inversion [bandw2i]

    Total rotation (in degree): 180
    DeltaOmega*DeltaT factor using -Mz: 0.734
• Calculate Bandwith for Refocusing -My [bandw2ry]

    Define Total rotation (in degree): 180
    DeltaOmega*DeltaT factor using -My: 0.882
• Calculate gammaB1max on Resonance [calcb1m]

    Length of pulse (in us): 10000
    Total rotation (in degree): 90
    Maximum gammaB1 (on resonance): 60.7419
    Corresponding 90 degree square pulse: 4115.78
• Calculate gammaB1max off Resonance [calcb1mo]

    Length of pulse (in us): 10000
    Total rotation (in degree): 90
   Offset (in Hz): 3000
    Maximum gammaB1 (off resonance): 85703.5
    Corresponding 90 degree square pulse: 2.91703
• Calculate average Power Level [calcpav]

    Amplitude relative to a square pulse of 100%: 0.411578
    Corresponding difference in dB: 7.71907
   Power relative to a square pulse of 100%: 0.169396
• Integrate Shape and compare to Square [integr]

    Integral ratio compared to a square pulse of 100%: 0.411578
    Corresponding difference in dB: -7.71907
• 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%: 0.411578
    Change of power level compared to level of hard pulse in dB: 56.726
 

 

90 degree Gaussian Shape   (in ms)	1	5	10	20	40	60	80	100
Corresponding 180 degree Gaussian Shape   (in ms) at the same power level	2	10	20	40	80	120	160	200
Corresponding 270 degree Gaussian Shape   (in ms) at the same power level	3	15	30	60	120	180	240	300
Maximum gammaB1   (on resonance) (in Hz)	607.4	121.5	60.7	30.4	15.2	10.1	7.6	6.1
Corresponding 90 degree  square pulse (in ms)	0.41	2.06	4.11	8.23	16.46	24.69	32.9	41.16
Change of power level   compared to level of a 10 us hard  90 degree pulse (in dB)	32.29	46.26	52.29	58.30	64.33	67.85	70.35	72.28

 

 

Amplitude relative to a   square pulse of 100%	0.411
Corresponding difference to a 100%   square pulse of the same duration (in dB)	7.71

 

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

The theoretical excitation and inversion profiles of a gaussian shaped pulse can be visualized from the NMRSIM program:

A) Gaussian shaped 90 degree pulse as a excitation element:

1. Select the corresponding File-->Experiment Setup-->Load from File ... menu.
2. Choose the profile.cfg configuration file.
3. Select the Go-->Run Experiment menu.
4. 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).
5. 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 3 and 4 steps to obtain the new profile.

B) Gaussian shaped 270 degree pulse as a excitation element:

1. Select the corresponding File-->Experiment Setup-->Load from File ... menu.
2. Choose the profile.cfg configuration file.
3. Set AW 2 to 270 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).
6. 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.

C) Gaussian shaped 180 degree pulse as a inversion element:

1. Select the corresponding File-->Experiment Setup-->Load from File ... menu.
2. Choose the profile180.cfg configuration file.
3. Select the Go-->Run Experiment menu.
4. 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).
5. The duration of the shaped pulse can be modified by changing the P5 parameter (by default, 10 ms) in the Go-->Check Experiment parameters menu. Repeat the 3 and 4 steps to obtain the new profile.

D) Gaussian shaped 180 degree pulse as a refocussing element:

1. Select the corresponding File-->Experiment Setup-->Load from File ... menu.
2. Choose the spfge.cfg configuration file.
3. Select the Go-->Run Experiment menu.
4. 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, 10 ms) in the Go-->Check Experiment parameters menu. Repeat the 3 and 4 steps to obtain the new profile.