Determination of the quadrupole coupling constant from a featureless NMR lineshape
In order to cancel the FID of the central transition following the second pulse, we should apply the double-quantum (DQ) filtered Solomon echo sequence. That is, only DQ coherences generated by the first pulse are converted back to -1Q coherence as echoes of satellite transitions by the second pulse. The duration tau2 between the two pulses must be shorter than that of the central-transition FID. Solomon echoes are satellite-transition signals. In contrast to the other echo experiments, Solomon echoes are observed in the two channels in quadrature phase of the receiver. The observation of these echoes requires the optimization of the two pulse-lengths p1 and p2.
The echo amplitudes in this experiment are a product of two functions: the excitation function A(p1) that depends on p1 and the conversion function B(p2) that depends on p2. In fact A(p1) is a sum of two coherences generated by the first pulse.
The left part of the simulation panel indicates the physical parameters. It is preset for a typical experiment on a spin I = 3/2 in a powder. You can introduce your own values.
In the upper choice box, 2-Quantum means DQ filtered pulse sequence. There is only one item in this choice box.
First, with the lower choice box we select one of the two types
of echo amplitude calculation:
(1) A(p1)B(): the variable pulse-length is p1 and the constant pulse-length is p2;
(2) A()B(p2): the constant pulse-length is p1 and the variable pulse-length is p2.
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 nature of the echo and its position with the two choice boxes above the RUN button. Since the echoes are detected in the two channels in quadrature of the receiver, after pressing the RUN button we use the check buttons to choose the real or the imaginary parts of the echo amplitude.
The following applet is initialized for the satellite echo amplitude A()B(p1) of a spin I = 3/2 in a powder, excited by the double-quantum filtered Solomon echo sequence; this echo is located at tau4 = tau2; the pulse length p1 is equal to 5 µs and p2 increases from 0 to 10 µs by 0.5 µs step. The experimental line intensities are identical to the simulated ones.
JDK1.0.2 applet for DQ Solomon echo nutation NMR applied to a powder