By counting the number of such X-rays while scanning the frequency of the laser pulse, the team could make a very precise measurement of the photon energy required to drive the 2s-2p transition.
After that is the transition region a few hundred to a few thousand miles or kilometers thick, which is heated by the corona above it and sheds most of its light as ultraviolet rays.
在这之外是厚度为几百到几千公里的过渡区，它由在其上的日冕加热，并发射大部分光和紫外线。
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Calculations suggest, for instance, that in the nucleus of the isotope thorium-229 is a transition that should emit ultraviolet rays.