Powder.m

Static powder interface to pulse sequences. Generates a Liouvillian superoperator, the initial state and the coil state, then passes them on to the pulse sequence function.

Syntax

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

Arguments

 pulse_sequence     - pulse sequence function handle. See the
                      experiments directory for the list of
                      pulse sequences that ship with Spinach.
 
 parameters.spins   - a cell array giving the spins that the
                      pulse sequence works on, in the order
                      of channels, e.g. {'1H','13C'}

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

 parameters.grid    - name of the spherical averaging grid
                      file (see the grids directory in the
                      kernel).

 parameters.rframes - rotating frame specification, e.g.
                      {{'13C',2},{'14N,3}} requests second
                      order rotating frame transformation
                      with respect to carbon-13 and third
                      order rotating frame transformation
                      with respect to nitrogen-14. When
                      this option is used, the assumptions
                      on the respective spins should be
                      laboratory frame.

 parameters.needs   - a cell array of strings specifying ad-
                      ditional information required by the
                      sequence:

                      'zeeman_op' - Zeeman part of the Hami-
                      ltonian in the laboratory frame, to be
                      placed into parameters.hzeeman and sent
                      to the pulse sequence

                      'aniso_eq' - thermal equilibrium is re-
                      computed using the full anisotropic Ha-
                      miltonian at each orientation, and sent
                      to pulse sequence via parameters.rho0

  parameters.*      - additional subfields may be required by
                      the pulse sequence - check its documen-
                      tation page 

  assumptions       - context-specific assumptions ('nmr', 'epr',
                      'labframe', etc.) - see the pulse sequence
                      header for information on this setting.

Outputs

This function returns a powder average of whatever it is that the pulse sequence returns. If a structure is returned by the pulse sequence, the structures are powder averaged field-by-field.

Examples

There are over 100 examples using this context in the example set. The following cases are representative:

dnp_solids/crosspol_powder_static_1.m - electron-nuclear cross-polarisation DNP

esr_solids/hyscore_nitroxide_powder.m - HYSCORE spectrum of a nitroxide radical

giant_spin/triple_dy_eqmag_temp.m - temperature dependence of equilibrium magnetisation in a dysprosium cluster

nmr_solids/cp_powder_match_3.m - Hartmann-Hahn matching condition under MAS

Notes

1. THIS IS FOR STATIC POWDERS - use singlerot.m for MAS simulations.
2. Arbitrary order rotating frame transformation is supported, including infinite order. See the header of rotframe.m for further information.
3. The function supports parallel processing via Matlab's Distributed Computing Toolbox - different system orientations are evaluated on different labs.

See also

crystal.m, liquid.m, roadmap.m, singlerot.m, doublerot.m, imaging.m, gridfree.m, floquet.m

Version 2.2, authors: Ilya Kuprov, Luke Edwards