Overtone soft pulse-acquire experiment with frequency-domain acquisition.
The function performs a soft pulse followed by frequency-domain acquisition at the overtone frequency. Because time-domain overtone spectroscopy is difficult (see http://dx.doi.org/10.1039/C4CP03994G for details), this mode of acquisition is preferable in practice. Simulations assumptions should be set to 'qnmr'.
parameters.sweep - vector with two elements giving the spectrum frequency extents in Hz around the overtone frequency parameters.npoints - number of points in the spectrum parameters.rho0 - initial state parameters.coil - detection state parameters.Lx - X Zeeman operator on the quadrupolar nucleus parameters.rf_frq - pulse frequency offset from the overtone frequency on the quadrupolar nucleus, Hz parameters.rf_pwr - pulse power on the quadrupolar nucleus, Hz parameters.rf_dur - pulse duration, seconds parameters.method - 'average' uses the average Hamiltonian theory, 'fplanck' uses Fokker-Planck formalism for the calculation of the pulse evolution. H - Hamiltonian commutation superoperator R - unthermalised relaxation superoperator K - chemical kinetics superoperator
The function returns the populations of the detection state at the frequencies specified.
The following 15N overtone spectrum is produced by examples/nmr_overtone/mas_valine_2.m example file:
- Relaxation must be present in the system dynamics, or the matrix inverse-times-vector operation performed by the frequency domain detection module would fail to converge. The relaxation superoperator should not be thermalised.
- Relaxation theory is not applied during the pulse.
- Average Hamiltonian and Fokker-Planck pulses produce signals in different phases. We are trying to figure out why, but it looks non-trivial. The average Hamiltonian theory option is faster.
- Irrespectively of the pulse algorithm option selection, the magic angle spinning is always handled with the Fokker-Planck formalism.