# deer_4p_soft_hole.m

Pulse diagnostics for the four-pulse DEER/PELDOR pulse sequence. This function shows how soft pulses affect the magnetisation of the sample. It is a hypothetical experiment where a soft pulse specified by the user is performed, immediately followed by an ideal pi/2 pulse on all spins followed by infinite-bandwidth time-domain detection.

## Syntax

    fids=deer_4p_soft_hole(spin_system,parameters,H,R,K)


## Arguments

   parameters.pulse_frq  - frequencies for the four
pulses, Hz

parameters.pulse_pwr  - power levels for the four

parameters.pulse_dur  - durations for the four
pulses, seconds

parameters.pulse_phi  - initial phases for the four

parameters.pulse_rnk  - Fokker-Planck ranks for the
four pulses

parameters.offset     - receiver offset for the time
domain detection, Hz

parameters.sweep      - sweep width for time domain
detection, Hz

parameters.npoints    - number of points in the free
induction decay

parameters.rho0       - initial state

parameters.coil       - detection state

parameters.method     - soft puse propagation method,
'expv' for Krylov propagation,
'expm' for exponential propa-
gation, 'evolution' for Spin-
ach evolution function

H  - Hamiltonian matrix, received from context function

R  - relaxation superoperator, received from context function

K  - kinetics superoperator, received from context function


## Outputs

   fids  - four free induction decays that should be apo-
dised and Fourier transformed


## Examples

A good case is the first figure produced by examples/esr_solids/soft_4_pulse_deer_2e.m example file, reproduced below.

## Notes

For the method, start with 'expm', change to 'expv' if the calculation runs out of memory, and use 'evolution' as the last resort.