2D HYperfine Sub-level CORrElation
2D HYSCORE is essentially a two dimensional ESEEM experiment in which correlation is transferred from one electron spin manifold to another.
In a HYSCORE experiment, the time between the second π/2 and π pulse is varied in one dimension and the time between the π and third π/2 pulse is varied in a second dimension. A two dimensional FT gives the sample data below.
2D-HYSCORE Spectrum of a Coal Standard Sample
As in an ESEEM experiment, the peaks observed are essentially an NMR spectrum of nuclei that are coupled to the electron. HYSCORE allows one to take a complicated ESEEM spectrum and extend the data into a second dimension Peaks appearing in the upper right and lower left quadrants typically arise from nuclei in which the hyperfine coupling is less than the larmor frequency. They appear at the larmor frequency, separated by the hyperfine coupling. Peaks from nuclei in which the hyperfine interaction is greater than the larmor frequency appear in the upper left and lower right quadrants. The HYSCORE spectrum can get very complicated for nuclei with a spin of I > 1/2 with many peaks arising from the complication of additional nuclear zeeman and quadrupole levels. Even with the complexity of the spectra, HYSCORE on systems with multiple nuclei can make ESEEM spectra that would be difficult or impossible to interpret much more manageable.