Duration of the excited state of complex molecules in the gas phase under anti-Stokes excitation

The dependence of the mean durations of fluorescence of rarefied complex molecule vapors is investigated by a fluorometric method according to the absorption spectrum under anti-Stokes excitation. Some phthalimide derivatives were used as subjects of the investigation. It has been established that the mean duration of fluorescence for the compounds studied remains constant in the whole range of anti-Stokes excitation investigated. This agrees with the results of investigating the dependence of the fluorescence quantum yield in the gas phase on the exciting light frequency according to data in the literature. The temperature dependence of the glow duration under anti-Stokes excitation is the same as in the contiguous Stokes domain. It is known that the true stores of vibrational molecule energy in the upper electron state characterizes the effective excitation energy E_ef^* which differs considerably from the energy of an exciting quantum and is constant in the anti-Stokes domain for the compounds investigated, in the case of rarefied vapors. The independence of from established confirms the statement that molecules excited in the anti-Stokes domain do not differ in their properties from molecules excited in the adjacent long-wave Stokes domain, under conditions of constant vibrational energy.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 25–29, April, 1973.