grad_pulse.m

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Emulates the effect of a gradient pulse on the sample average density matrix using Edwards formalism. It is assumed that the effect of diffusion is negligible, that the gradient is linear, and that it is antisymmetric about the middle of the sample.

Syntax

    rho=grad_pulse(spin_system,rho,g_amp,s_len,g_dur,s_fac)

Arguments

        rho   - spin system state vector

          L   - system Liouvillian

      g_amp   - gradient amplitude, Gauss/cm

      s_len   - sample length, cm

      g_dur   - gradient pulse duration, seconds

      s_fac   - gradient shape factor, use 1 for
                square gradient pulses

Outputs

     rho - spin system state vector, integrated over
           the spatial coordinate

Examples

See examples/fundamentals/gradient_test_1.m file for an example of using this function.

Notes

  1. WARNING This function integrates over the spatial coordinate after the gradient pulse is completed - subsequent gradient pulses would not refocus the magnetisation that this function removed because it is removed mathematically. If your experiment has multiple gradient pulses, you must model the spatially distributed spin dynamics explicitly using imaging.m context.
  2. More information on the subject is available in Luke's paper (http://dx.doi.org/10.1016/j.jmr.2014.01.011).

See also

grad_sandw.m, imaging.m


Version 2.2, authors: Luke Edwards, Ilya Kuprov