Aquantum system has three energy levels, so three wavelengths appear in its emission spectrum. the shortest observed wavelength is 278 nm ; light with a 454 nm wavelength is also observed. what is the third wavelength?

The wavelength emitted is indirectly proportional to the difference in the change in the energy level. For the wavelength 278 nm the change in energy level is significantly high. Further change in energy level is indicated by 454nm light but the difference in energy level for this wavelength to be emitted  is not greater than the previous one. There is a possibility that these subsystems have now very low energy which should result in wavelengths ranging from 700 to 900 nm. There is another possibility that there is some metastable subsystems in the system which may cause LASER emission.