# Gridfree.m

Fokker-Planck magic angle spinning and SLE context. Generates a Liouvil- lian superoperator and passes it on to the pulse sequence function, which should be supplied as a handle. Syntax:

    answer=fplanck(spin_system,pulse_sequence,parameters,assumptions)


where pulse sequence is a function handle to one of the pulse sequences located in the experiments directory, assumptions is a string that would be passed to assume.m when the Hamiltonian is built and parameters is a structure with the following subfields:

  parameters.rate     - spinning rate in Hz

  parameters.axis     - spinning axis, given as a normalized
3-element vector

  parameters.spins    - a cell array giving the spins that
the pulse sequence involves, e.g.
{'1H','13C'}

  parameters.offset   - a cell array giving transmitter off-
sets in Hz on each of the spins listed
in parameters.spins array

  parameters.max_rank - maximum D-function rank to retain in
the solution (increase till conver-
gence is achieved, approximately
equal to the number of spinning si-
debands in the spectrum)

  parameters.tau_c - correlation times (in seconds) for rotational dif-
fusion under 'sle' option. Single number for iso-
tropic rotational diffusion, two for axial and
three for rhombic rotational diffusion. Other in-
teractions and coordinates are assumed to be spe-
cified in the rotational diffusion tensor eigenframe.


Additional subfields may be required by the pulse sequence. The parameters structure is passed to the pulse sequence with the following additional parameters set:

  parameters.spc_dim  - matrix dimension for the spatial
dynamics subspace

  parameters.spn_dim  - matrix dimension for the spin
dynamics subspace


This function returns the powder average of whatever it is that the pulse sequence returns.

Note: the choice of the Wigner function rank truncation level depends on the spinning rate (the slower the spinning, the greater ranks are required).

Note: rotational correlation times for SLE go into parameters.tau_c, not inter.tau_c (the latter is only used by the Redfield theory module).

Note: the state projector assumes a powder -- single crystal MAS is not currently supported.