The Gaussian cascade shapes were proposed by Bodenhausen and they has been largely used as powerful selective excitation, selective refocusing and selective inversion elements in many NMR experiments.

The Gaussian cascade pulses can be defined in the SHAPE tool.

The original gaussian cascade pulses (90 degree G4 and 180 degree G3 pulses) consist of superpositions of k time-shifted Gaussians pulses with optimized widths and peak amplitudes ( 90CPL469 ).

On the other hand, universal or general rotation pulses (90 degree Q5 and 180 degree Q3 cascade pulses) were proposed based on the quaternion description ( 92JMR135-97 ). Such pulses perform well regardless of the initial condition to which they are applied.

Application: frequency-selective decoupling using a G3 inversion pulse in an MLEV-16 cycle ( 92JMR604-100 ).

More details in Tutorial: Defining a Gaussian Cascade Shape.

The theoretical excitation and inversion profiles of the Gaussian Cascade shaped pulses can be visualized from the NMRSIM program:

A) G4 (or Q5) shaped 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 the shape to G4.shp (or Q5.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).
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.

 
B) G3 (or Q3) shaped pulse as a inversion element:
1. Select the corresponding File-->Experiment Setup-->Load from File ... menu.
2. Choose the profile180.cfg configuration file.
3. Set the shape to G3.shp (or Q3.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).
6. 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.

 
C) G3 (or Q3) shaped pulse as a refocussing element:
1. Select the corresponding File-->Experiment Setup-->Load from File ... menu.
2. Choose the spfge.cfg configuration file.
3. Set the shape to G3.shp (or Q3.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).
6. 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.