slowpass.m

Slow passage detection - calculates spectrum values at the user specified frequency positions using the Fourier transform of the Liouville - von Neumann equation. The biggest advantage over the fid+fft style detection is easy parallelization and the possibility of getting spectrum values at specific frequencies without recalculating the entire free induction decay.

Syntax

spectrum=slowpass(spin_system,parameters,H,R,K)

Arguments

parameters.sweep vector with two elements giving

                            the spectrum frequency extents
                            in Hz

    parameters.npoints       number of points in the spectrum

    parameters.rho0          initial state

    parameters.coil          detection state

    H  - Hamiltonian matrix, received from context function

    R  - relaxation superoperator, received from context function

    K  - kinetics superoperator, received from context function

Outputs

spectrum - the spectrum of the system with the specified

               starting state detected on the specified coil
               state within the frequency interval requested

Note: relaxation must be present in the system dynamics, or the
      matrix inversion operation would fail to converge. The re-
      laxation matrix R should *not* be thermalized.

ilya.kuprov@weizmann.ac.il

Examples

The 14N overtone MAS spectrum of glycine recorded using this method (examples/nmr_overtone/mas_glycine_1.m) appears below. FID+FFT simulation in this system is much slower.

Notes

Relaxation must be present in the system dynamics, or the matrix inversion operation would fail to converge. The relaxation matrix R should *not* be thermalized.

See also

acquire.m, fieldscan_enlev.m, fieldscan_magn.m, fieldsweep.m, rapidscan.m

Version 2.3, authors: Ilya Kuprov