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

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_mag.m, fieldsweep.m, rapidscan.m

Version 2.3, authors: Ilya Kuprov