EasySpin forum

I collected an EPR spectrum of DMPO-OH (produced by photolyzing H2O2 in water with DMPO) to practice fitting in Easyspin. I adapted the code from the fitting example on the YouTube channel and used the literature g-value of 2.0062, allowing for a variation of 0.004. I was satisfied with the fit, but the best fit g-value turned out to be 2.00829. I am confused as to why it is so different from the reported value. Does it have to do with the instrument?

It might be that the magnetic field on the instrument is not calibrated accurately enough.

Also keep in mind that g-values can depend on the nanoenvironment of the radical, for example the solvent, and on the state (liquid vs. solid).