redor.m

Rotational-echo double-resonance (REDOR) experiment with ideal hard pi pulses. The observed channel is refocused once per rotor period, and the dephasing channel is pulsed at rotor-period boundaries. The sequence reports the full rotational echo, the dephased echo, and their difference as a function of the number of rotor cycles. To be called from singlerot context. The Liouvillian is assembled as L=H+1i*R+1i*K and the requested nuclei are removed analytically by decouple.m. Two trajectories are propagated side by side from the same initial condition: over each rotor period both are stepped through a half period, hit with an ideal pi pulse on the observed channel at the phase given by parameters.refocus_phase, stepped through the second half period, and detected; the dephased trajectory additionally receives an ideal pi pulse on the dephasing channel at the end of each rotor period, cycling through the phases in parameters.pulse_phase. All operators are lifted into the Fokker-Planck space with a Kronecker product against a unit matrix of dimension parameters.spc_dim. Echo intensities are accumulated at every rotor-period boundary, including the zero-time point, and the requested cycle counts are picked out at the end.

Further information in:

    https://doi.org/10.1016/0022-2364(89)90280-1
      https://doi.org/10.1006/jmre.2000.2128

Syntax

    redor_curve=redor(spin_system,parameters,H,R,K)

Parameters

    parameters.spins        - observed and dephasing spins,
                              e.g. {'13C','15N'} for 13C{15N}
                              REDOR

    parameters.ncycles      - row vector with numbers of rotor
                              cycles in the REDOR evolution time

    parameters.rate         - MAS rate in Hz

    parameters.rho0         - initial state vector, usually
                              transverse magnetisation on the
                              observed spin

    parameters.coil         - detection state vector, usually on
                              the observed spin

    parameters.decouple     - nuclei to decouple analytically
                              during REDOR evolution, supplied as
                              a cell array of isotope strings

    parameters.refocus_phase - phase of the observed-channel pi
                              refocusing pulses, radians; defaults
                              to 0

    parameters.pulse_phase  - phases of the dephasing-channel pi
                              pulses, radians; the vector is cycled
                              through the pulse train, and defaults
                              to [0 pi/2]

    H  - Hamiltonian matrix, received from context function

    R  - relaxation superoperator, received from context function

    K  - kinetics superoperator, received from context function

Outputs

    redor_curve(1,:)        - full echo S0, with observed-channel
                              refocusing pulses only

    redor_curve(2,:)        - dephased echo S, with observed-channel
                              refocusing and dephasing-channel pi
                              pulses

    redor_curve(3,:)        - REDOR difference, S0-S

Notes

The function is only available in sphten-liouv formalism, and the two entries of parameters.spins must not appear in parameters.decouple.

See also

cn2d_dq.m, cn2d_sq.m, cp_acquire_soft.m, cp_contact_hard.m, cp_contact_soft.m, dante.m, fslghetcor.m, mqmas.m, nqr_pa.m, pdsd.m, respiration.m, wise.m, Built-in_experiments

Version 2.13, authors: Ilya Kuprov