rsequence.m

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R-sequences described in Malcolm Levitt's review (https://doi.org/10.1002/9780470034590.emrstm0551). The notation below is based on RN_{n}^{\nu}.

Syntax

    [phases,pulse_amp,pulse_dur]=rsequence(n_rotor_periods,n_blocks_per_period,...
                                           phase_factor,n_cycle_repeats,mas_rate,...
                                           element_type,supercycle_type)

Arguments

  n_rotor_periods     -  "small n" symmetry number, gives number of
                          rotor periods required in the R symmetry

  n_blocks_per_period -  "capital n" symmetry number, gives the number of
                          R elements contained within the R symmetry

  phase_factor        -  "nu" to calculate the alternating phase in the 
                          R sequence:

                         180*nu/N = 180*phase_factor/n_blocks_per_period

  n_cycle_repeats     -  number of times the full R sequence is applied 
                 
  mas_rate            -  rotor spinning rate, Hz

  element_type        -  R element needs to be an inversion pulse. Common
                         R elements are:

                          '180_pulse'   : simple inversion pulse

                          '90270_pulse' : composite inversion pulse

  supercycle_type     -  The R sequence can be repeated multiple
                         times in combination with supercycles, for
                         improved performance, removal of undesired 
                         higher order terms. If the he unmodified R
                         is denoted [phase], this can either be in-
                         verted, [-phase], or have an overall phase
                         added to it, [phase]_addph.

                         Common supercycles are:

                          'hetero_single_quantum' 
                          [phase]_0:[-phase]_0:[phase]_120:[-phase]_120:[phase]_240:[-phase]_240

                          'homo_double_quantum_nucycle'
                          [phase]_0:[-phase]_0

                          'homo_double_quantum_nupicycle'
                          [phase]_0:[-phase]_0:[-phase]_180:[phase]_180

Outputs

  phases    - the sequence of pulse phases, radians

  pulse_amp - RF nutation frequency in rad/s, a scalar because
              R-sequences are phase-modulated

  pulse_dur - duration of the pulses in the sequence element,
              a vector with the length matching the number of
              pulses in the sequence element (seconds)

See also

Shaped pulses and gradients


Version 2.7, authors: Marina Carravetta, Ilya Kuprov