HYSCORE powder spectrum outline.

nucfrq2d(Sys,B0)
nucfrq2d(Sys,B0,tauvec)

nucfrq2d computes and plots the outline of a HYSCORE powder spectrum. Peaks positions are accurate, but all peak intensities are set to 1. The plot thus only shows correlation patterns.

Sys is the spin system structure defining the spin Hamiltonian. In Sys, the electron spin must be 1/2.

B0 gives the magnitude of the external magnetic field, in mT.

tauvec is a vector of tau values, in microseconds. It is used to plot blind spot regions, where the ESEEM signal is suppressed.

The plot shows two octants as is standard for HYSCORE spectra and displays all nuclear frequency correlations in color. Peaks that correlate frequencies from the α electron manifold on the horizontal axis with β frequencies on the vertical axis are in green, the β-α correlations are in red.

If tauvec is given, a gray-shaded background indicating peak suppression regions (blind spots) is shown. White indicates no suppression, the darker the gray the stronger the suppression.

Correlation plots can be quite aesthetic. For a fantasy system containing one electron and one ¹⁴N nucleus

Sys.g = 2;
Sys.Nucs = '14N';
Sys.A = 2 + [-1 -1 2]*2;  % MHz
Sys.Q = [-1.2 -0.8 2]*1.2;  % MHz
 
nucfrq2d(Sys,350);  

To observe the peaks due to weakly coupled hydrogens, one best uses several tau values related to the Larmor frequency of hydrogen

 Sys.g = 2;
 Sys.Nucs = '1H';
 Sys.A = [-1 -1 2]*4 + 2;   % MHz
 
 B0 = 350;   % mT
 nuL = larmorfrq(Sys.Nucs,B0);   % MHz
 tauvec = [1.5 2.1]./nuL;   % µs
 
 nucfrq2d(Sys,B0,tauvec)
 

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