I am happy to see you participating, and to see you genuinely making your best possible effort to keep the tagging system as close to optimal as possible!
It's hard to tell a priori how new tag names will be received. I predict that a lot of people will use transport and electron-diffraction. Not all diffraction is electron diffraction, so I can see the logic behind diffraction. Thermal-transport might be too specific (but I do not know yet so we might have to wait!). Certainly electron-transport and quantum-transport and exciton-transport are all excellent topics, and it might be better to have them all fit under one transport tag rather than having several.
In the spirit of keeping the number of tags low, maybe we only need one of the diffraction ones (and electron-diffraction is a strict subset of diffraction), however if others don't mind, I wouldn't mind keeping them for now and seeing how they are used. We still don't have many users, so it's hard to tell. We could visit this if we observe that 100% of the 50 questions on diffraction all end up being about electron-diffraction, or of 5 different types of diffraction get 10 questions each.
I have also added scattering to your atom scattering question, since I'm sure we'll be getting plenty of scattering questions.
If there's one thing you might be able to help us with, it is perhaps adding the Wiki for the tags you created, as we have made sure there is at least something for each tag appearing on the first page of this.