# Difference between revisions of "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 magnetization that it has defocused because it is wiped out 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

Version 2.2, authors: Luke Edwards, Ilya Kuprov