g(iso) and A(iso) of fast motion simulation

[Sidlaw]

Dear Stefan, I was recently confused on g and A values of "garlic" simluation of EPR spectrum of my mononuclear [Cu(II)(NNNO)] complex. Could you please tell me what is the relationship between g(iso) and g(xx), g(yy), g(zz) for "garlic" simulation of fluid samples? Also, relationship between A(iso) and A(xx), A(yy), A(zz)? Thanks a lot.

[Matt Krzyaniak]

garlic simulates fast motion isotropic spectra, The assumption is that your sample is tumbling fast enough such that all of the anisotropic interactions average out.
What this means is that if you know your full g tensor g = [g_x g_y g_z], in the fast motion regime what you observe is a spectrum centered at (g_x + g_y + g_z)/3, the average g value or g_iso. A similar case occurs with the hyperfine, a_iso = (A_x + A_y + A_z) /3.