Fluorescence lifetimes of the van der Waals clusters of octatetraene (S1)-rare-gas atoms: external heavy atom effect

Fluorescence lifetimes of the trans,trans-1,3,5,7-octatetraene-rare-gas van der Waals clusters formed in supersonic jet expansions are measured. The lifetimes show that the clusters with heavier atoms decay much more rapidly than those with lighter ones. This observation indicates that the external heavy atom effect manifests in the collisional relaxation of electronically excited polyenes in contrast to the previous observation in low-temperature matrices. The apparent contradiction is explained in terms of the difference in strength of interactions in the matrices and van der Waals complexes.