AIM: Determination of the quadrupole coupling constant from a featureless NMR lineshape
Launch the rotary-echo pulse applet with Java Web Start.
![Rotary-echo sequence for nutation NMR](rotary-echo.gif)
Despite the name of this sequence, we do not perform echo experiments because the signal is observed at the end of the second pulse.
Two rotary-echo sequences are presented:
X-(-X): {+X,-X}-acq(y)
Even-X: {+X,-X}-acq(y)
Even-X: {-X,-X}-acq(y)
These two sequences do not cancel spurious signals whereas the composite-pulse sequence does. On the other hand, if the two pulse-lengths are identical (p1 = p2), the X-(-X) sequence cancels signals with small and large quadrupolar coupling constants.
![This is an image. The applet is located at the bottom of the page. IMAGE: Rotary-echo parameters panel for nutation NMR](rotary-echo-panel.gif)
The left part of the panel indicates the parameters of the simulation. It is preset for a typical experiment on a spin I = 3/2 in a powder. You can introduce your own values.
First, we select the rotary-echo sequence with the upper choice box.
Then, we select the line intensity calculation with the lower
choice box:
(1) V-V: p1 and p2 vary identically;
(2) V-F: p1 varies and p2 remains constant;
(3) F-V: p1 remains constant and p2 varies.
When p1 = p2, only the parameters for p1 are required.
A constant pulse length should be provided in the MinLength field.
MinLength: the first variable pulse-length in µs
MaxLength: the last variable pulse-length in µs
Step: the increment of the variable pulse-length in µs
The following applet is initialized for the central-line intensity of a spin I = 3/2 in a powder excited by the X-(-X) rotary-echo sequence where the two pulse-lengths vary identically. The experimental line intensities are identical to the simulated ones.
Help for selecting all the simulated data of the line intensity text area in a JDK1.1.8 applet.