Asphaltene: FR and VP

[Tunneller]

Hi, I see many papers where EasySpin has been used successfully to compute spectra of vanadyl radicals within an asphaltene powder and also where there is also of combination of organic free radical with the vanadyl in the powder. I see an example where weighting of 90% VP and 10% FR matches data. Cool.

I'd like to do the same for a slowly rotating system of asphaltene macromolecules in oil, e.g tcorr = 1.e-7. I can rotate vanadyl with chili. Cool.

But if I have isotropic free radical with weight .1 and vanadyl with weight .9, then now I have a problem with chilli, because it is looking for hyperfine values for the free radical component.

Is there a way to model this, or at least "fake" it. Regards, John

[Tunneller]

I got it to work by giving the isotropic radical a "g' value of [2.0028 2.0029] and then garlic would run, which meant then I could run it as a multiple component system and I could run esfit too. Very nice.

But why chili not happy with isotropic system?

Regards, John

[Tunneller]

Aagh. This keeps coming back to bite me. I'm back to looking at the combination of both free radical and vanadyl radical inside a molecule and now want to look into rotational correlation, i.e. chili using a weighted combination of two spin systems.

Is there really no way to trick chili into modelling this? For garlic I got away with making gfactor of the FR very, very slightly anisotropic. But now for chili I have to have hyperfine spacing too.

Should I set the A for the free radical as something very, very small?

Regards, John

[Stefan Stoll]

I think it should be sufficient for chili if you give a slightly anisotropic g tensor for the organic radical.

In fact, there is no paramagnetic molecule with a perfectly isotropic g value! For modelling rotations, one always needs to enter the actual anisotropic g tensor.

garlic is a simplification that assumes the tumbling is infinitely fast.