3-spin order & SpinachGUI

[teleanuflorin]

Greetings Prof. Kuprov,

I've stumbled upon a result from one of my notebooks (see attachment) that deals with the transfer of magnetization from one spin (K) in a three-spin system (I,S,K). Starting from Kx magnetization followed by CW irradiation on all three spins, the trajectory analysis function (trajan) shows the build-up of 3-spin order correlations even though the only scalar-coupled spins in the system are I and S. After analyzing the effect of dipolar coupling, I've come to the conclusion that Kx can not be mixed with any 2-spin order state solely by incoherent mechanisms. Thus, how come 3-spin orders rise in such experiment?

The second question concerns the development of SpinachGUI. It seems like a great pedagogical tool to teach students about relaxation interactions, euler anglers, tensors etc., but it is currently missing from the wiki page (it's a dead link - http://spindynamics.org/Spinach-GUI.php). What happened to it?

Thank you so much for developing such a complete program. It helps me a lot with my Ph.D.

Cheers,
Florin Teleanu, RO

[kuprov]

Firstly, the rlx_keep is not right - you are using lab frame relaxation superoperator in the rotating frame. You should use 'secular'. This rarely matters though, but technically it must be done.

Your three-spin order comes from cross-correlated relaxation (see the nice review here http://repository.ias.ac.in/722/1/350.pdf). Remember that the implementation of Redfield theory in Spinach is by numerical brute force - it automatically picks up all relaxation processes, both known and unknown. In your case, it looks like you have a DD-DD cross-correlation that converts Lz to LzSzMz. I don't think anyone ever looked at this process - check the literature and write a paper on it!

You can see that process disappearing if you set inter.rlx_keep='diagonal' - that removes all cross-relaxation and cross-correlation processes from the relaxation superoperator.

As for the GUI, we could not get its development funded and it fell behind the rest of Spinach. I can give you access to the source code if you wish - it's Visual Studio / OpenGL, do with it what you like.

[teleanuflorin]

Thank you so much for your thorough reply. It makes sense now. I will look further into it and hopefully will come up with nice results.

As for the GUI, I found a repository on GitHub (https://github.com/spinachgui/spinachgui). Is it still relevant this one? If not, can you send me the version you're talking about?

Thanks again. Wish you many more prosperous days ahead

Florin

[kuprov]

No, that one isn't even us - something old and abandoned. I'll send you access credentials by email. If you end up making any useful changes, please commit them to that repository.