Conclusion

The analysis of photophysical constants allows to make the following basic conclusions:

1. The radiating channel of decay of state S₁* in anion is dominant, while in the neutral form probability of a crossing of a molecule in triplet states is great, so the intercrossing constant between the first singlet and fifth triplet states (K_ST = 10⁹ s^-1) is comparable on magnitude to a constant of radiative decay of a molecule from S₁* (10⁸ s^-1).
2. In the cation form at excitation of quantum of light < 250 nm singlet - triplet conversion between S₄* and T₆* states is probable.
3. In tautomeric form np * state is located in the region ~ 300 nm, that by using the excimer laser with a wavelength of excitation 308 nm results in reduction on efficiency of generation of ethanol solutions 4MU [7] because of the effective intercrossing conversion between S₃* and T₇* energy levels.