While reading the following article,
- Elizaveta A. Suturina, Kevin Mason, Carlos F. G. C. Geraldes, Ilya Kuprov, David Parker, Beyond Bleaney's theory: experimental and theoretical analysis of periodic trends in lanthanide-induced chemical shift, Angewandte Chemie, September 25, 2017
I came across the term eigenframe, which I am unfamiliar with. What is an eigenframe?
Here is the context in which it was used:
In particular, pseudo contact chemical shifts (PCS) induced by lanthanide complexes are commonly described by McConnell's long-range relation (SI units), $$ \delta^{PCS} = \frac{1}{12\pi r^3}[\chi_{ax}(3\cos^2 \theta -1)+3\chi_{rh}\sin^2\theta \cos2\phi]$$ where $\theta, \phi, r$ are the polar coordinates of the nucleus relative to the lanthanide in the eigenframe of the molar magnetic susceptibility tensor, and $\chi_{ax}$ and $\chi_{rh}$ are axiality and rhombicity of the susceptibility tensor.
