It's added what you wrote!

Also I wanted to make a new addition of totally over-roasting Spice with the UV-Light.

Daylight in summer made 11 % N-Oxide over 2 days, but obviously I have no idea about intensity, which would even vary a lot throughout the day.

A strong UV Lamp would anyways easily surpass that and I could use even higher-energy light. Daylight has at maximum (or minimum if you want) ~ 320 nm light, more gets absorbed throughout the atmosphere. That one is making you get sunburned. So I wanted to absolutely toast that DMT and see if everything gets converted to N-Oxide or if there is a threshold and moreover if there is any other degradation happening, like radical-induced cleavage of that pyrrol ring maybe, analog to some biologic anti-oxidants like Melatonin?

Now I placed some DMT for 1 h at 250 nm. Intensity I cannot measure for now, but it should be more than 1000 W / m². But actually not much happened?? Then I tried less energy, 1 h at 320 nm and then 1 h at 370 nm. Maybe the formation of N-Oxide would only correspond to a lower energy level, but that is unlikely.

Some pictures are attached. Judged by eye that sun-oxidized looked much worse Therefore I didnt even dare to go to NMR.

Maybe need to do it even longer, but that sounds weird ... might need to do some UV dose calculation to compare to an 'average summer day' in my country.

It does have to be the correct wavelength of UV light to be absorbed - perhaps examining a UV/vis spectrum of DMT would help instruct towards which wavelength might be the most effective for this reaction. Or maybe it's the UV absorption of dioxygen that matters? And what about low level ozone formation? Even away from pollution sources ozone levels can get quite high through wind drift.

There are a lot of variables to be controlled for.

So I think as you say the Oxygen is more likely to be the limiting factor here.

The absorption of DMT indicates where the chromophor (structure elements that are responsible for a certain absorption) would most likely to get into the excited state, but for N-Oxide formation it would most likely not make a difference, as that reaction would be just limited to the NMe2 + excited Oxygen. So Oxygen has to get from singulet to the excited triplet state and the chance for this transition is just getting higher with increasing UV strength as it also happens throughout our atmosphere at certain km heights. So I guess still the formation of N-Oxide would be strongest at 250 nm?

Apart from this the UV Spectrum also would mostly account for this wavelength if the Chromophor would be involved.

Based on what we all receive from sun I was pretty convinced that the maximum energy is 320 nm of light reaching the ground. So even if no spectrum is taken into account then 320 and 370 nm should be fine for some conversion?

But actually I was more interested into how the Chromophor itself could be decomposed, just like with Melatonin. In that case 250 nm would still be the best guess, there is no Mercury Lamp excitation wavelength that is exactly 280 nm. But maybe actually a product formed by some ring cleavage would not get oily so maybe what I have is already cleaved that way? Maybe should still analyze that thing, even if it looks yellowish crystalline.