It is probably safe to predict that the future of chemistry is linked to the excited states of molecules and to other short lived species, ions and free radicals. Molecules have only one ground state but many excited states. However large the scope of normal, ground state chemistry might be, above and beyond it lies the world of excited states, each one having its own chemis try. The electronic transitions leading to the excited states, either discrete of continuous, are examined in molecular elec tronic spectroscopy. Electronic spectroscopy is the queen of all spectroscopies: for if we have...