# Dnp field scan.m

Magnetic field scan steady-state DNP experiment.

## Description

Returns the steady-state population of the user-specified state as a function of magnetic field.

## Syntax

    answer=dnp_field_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      -   microwave frequency, Hz

parameters.fields      -   a vector of B0 field values, T

parameters.rho_eq      -   thermal equilibrium state

parameters.coil        -   detection state vector or a horizon-
tal stack thereof

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
applied magnetic field


## Examples

Cross effect in a system with two spin-1/2 electrons (cross_effect_field_scan_1.m example file in examples/dnp_solids directory):

Solid effect in a system with a spin-7/2 gadolinium ion (solid_effect_field_scan_1.m example file in examples/dnp_solids directory):

## Notes

1. The relaxation superoperator supplied to this function should NOT be thermalized.
2. Thermal equilibrium state is assumed to be the same at all fields in the sweep. Do not use this function for broad magnetic field sweep experiments.
3. Backslash method is recommended for small spin systems and GMRES method for large ones.
4. This function can be made to run on GPUs. If you would like that functionality added, send an email to Ilya Kuprov.