Four-pulse DEER/PELDOR pulse sequence. The sequence uses soft pulses computed with the Fokker-Planck formalism.
parameters.pulse_frq - frequencies for the four pulses, Hz parameters.pulse_pwr - power levels for the four pulses, rad/s parameters.pulse_dur - durations for the four pulses, seconds parameters.pulse_phi - initial phases for the four pulses, radians parameters.pulse_rnk - Fokker-Planck ranks for the four pulses parameters.p1_p2_gap - time between the end of the first and the start of the second pulse, seconds parameters.p2_p4_gap - time between the end of the second the start of the third pulse, seconds parameters.p3_nsteps - number of third pulse posi- tions in the interval between the first echo and the fourth pulse parameters.echo_time - time to sample around the ex- pected second echo position parameters.echo_npts - number of points in the second echo discretization 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
echo_stack - DEER echo stack, a matrix with p3_nsteps echoes with echo_npts points each
A number of complete examples for two- and three-electron systems are given in examples/esr_solids folder. A good way to proceed (soft_4_pulse_deer_2e.m example file) is to look at how the pulses affect the system:
then to inspect the echo stack as a function of the pump pulse position:
and finally to inspect the principal components of the echo stack. The most prominent component is the DEER trace, the other components come from the finite size of the spherical integration grid.
- For the method, start with 'expm', change to 'expv' if the calculation runs out of memory, and use 'evolution' as the last resort.
- Simulated echoes tend to be sharp and hard to catch because simulation does not have distributions in experimental parameters. Fourier transforming the echo prior to integration is recommended.
- The time in the DEER trace refers to the second pulse insertion point, after end of first pulse.
Version 2.4, authors: Ilya Kuprov