AIM: Determination of the quadrupole coupling from a featureless NMR lineshape
Launch the Hahn echo applet with Java Web Start.
![Hahn echo sequence with pulse lengths p1 and p2 for nutation NMR](Hahn-echo-nutation.gif)
In the basic two-pulse Hahn echo sequence on half-integer quadrupole spins, the single-quantum coherences generated by the first pulse are refocused as echoes by the second pulse. The observation of these echoes, located at tau2 = tau1, requires the optimization of the two pulse-lengths p1 and p2.
An echo amplitude is a product of two functions. The first function A(p1), called the excitation function, depends on p1. The second function B(p2), called the conversion function, depends on p2.
![This is an image. The applet is located at the bottom of the page. IMAGE: Parameters for the simulation of Hahn echo amplitude in nutation NMR](nmr-panel.gif)
The left part of the simulation panel indicates the physical parameters. It is preset for a typical experiment on a spin I = 3/2. You can introduce your own values.
First, we should select with the choice box one of the three types
of calculation available:
(1) A(p1)B(): the echo amplitude when p1 is variable and
p2 is constant;
(2) A()B(p2): the echo amplitude when p1 is constant and
p2 is variable;
(3) B(p2): the conversion function.
The first two cases could be checked experimentally, whereas the last
case is a theoretical result.
When a pulse length is constant, it 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
Then, we select the observed coherence, shown in the text-area above the RUN button.
The following applet is initialized for the conversion function of the central-transition Hahn echo amplitude B(p2) of a spin I = 3/2 in a single crystal. 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.