# Dnp freq scan.m

From Spinach Documentation Wiki

Microwave frequency scan steady-state DNP experiment.

## Description

Returns the steady-state population of the user-specified state as a function of microwave frequency.

## Syntax

answer=dnp_freq_scan(spin_system,parameters,H,R,K)

This function should normally be called via powder.m or crystal.m wrapper.

## Arguments

parameters.mw_pwr - microwave power, Hz parameters.mw_frq - row vector of microwave frequencies, rad/s parameters.rho_eq - thermal equilibrium state parameters.coil - detection state vector or a horizon- tal stack thereof parameters.mw_oper - microwave irradiation operator parameters.ez_oper - Lz operator on the electrons parameters.method - 'backslash' to use Matlab's linear equation solver, 'gmres' to use ILU preconditioned GMRES H - Hamiltonian commutation superoperator R - unthermalised relaxation superoperator K - chemical kinetics superoperator

## Returns

answer - the projection of the equilibrium density matrix on the user-specified state as a function of the microwave frequency

## Examples

A simple TOTAPOL based Cross Effect DNP system, set to reproduce Figure 2b from http://dx.doi.org/10.1016/j.jmr.2011.09.047 (examples/dnp_solids/cross_effect_freq_scan_3.m);

Intensity differences are due to a different relaxation model and minor inconsistencies between the stated geometry and the interaction amplitudes used in the original paper.

## Notes

- The relaxation superoperator supplied to this function should NOT be thermalized.
- Backslash method is recommended for small spin systems and GMRES method for large ones.
- This function can be made to run on GPUs. If you would like that functionality added, send an email to Ilya Kuprov.

## See also

dnp_field_scan.m,masdnp.m,solid_effect.m

*Revision 3284, authors: Ilya Kuprov, Walter Kockenberger, Alexander Karabanov*