Double intersystem-crossing in naphthalene and 1-chloronaphthalene

Measurements of the fluorescence decay constant 1/tau(F) for naphthalene and 1-chloronaphthalene in ethanol as a function of temperature provide values for the intersystem-crossing rate constant k(IS)(T) expressed as K-IS(T) = K-IS degrees + A(IS) exp(-E-IS/RT). It is found that both k(IS)degrees and A(IS) are greater by a factor of similar to 40 in 1-chloronaphthalene and it is concluded that the temperature-dependen and temperature-independent components of the computed rate constant k(IS)(T) describe intersystem-crossing processes to upper and lower triplet states of these molecules.