# dnp_freq_scan.m

Microwave frequency scan steady-state DNP experiment. Returns the steady-state population of the user-specified states as a function of microwave irradiation frequency.

## Syntax

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


## Arguments

   parameters.mw_pwr       -   microwave power, rad/s

parameters.mw_frq       -   row vector of microwave frequ-
to the reference g-factor

parameters.g_ref        -   reference g-factor around which
frequency offsets are specified

parameters.rho0         -   thermal equilibrium state

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

parameters.ez_oper      -   Lz operator on the electrons

H - Hamiltonian matrix, received from context function

R - relaxation superoperator, received from context function

K - kinetics superoperator, received from context function


## Outputs

   dnp    -  an array of the steady state amplitudes of the
states specified in parameters.coil as at each
of the microwave frequencies supplied


## Examples

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

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

1. The relaxation superoperator supplied to this function should NOT be thermalized.
2. Backslash method is recommended for small spin systems and GMRES method for large ones.