PHOTODISSOCIATION OF JET-COOLED EXCIMER IN MOLECULAR CLUSTERS OF 1-CYANONAPHTHALENE AND ITS DEUTERATED COMPOUND

The excimer formation and photodissociation in jet-cooled molecular cl usters of 1-cyanonaphthalene (1-CNN) and its deuterated compound (1-CN N-d(7)) were investigated. The jet-cooled excimer fluorescence was obs erved in the excitation cluster band (n greater than or equal to 4) of 1-CNN-d7 as well as of 1-CNN. The excitation of the excimer at 700-75 0 nm results in a considerably strong depletion of the excimer fluores cence and a simultaneous fragment fluorescence of the clusters at 335- 350 nm. An excimer depletion spectrum was observed at 700-750 nm from the wavelength dependence of the depletion laser of the fragment inten sity. Comparison of the excimer depletion spectrum of the jet-cooled c luster with that of the transient absorption of the excimer in solutio n suggests that the excitation into the upper state of the excimer ind uces the photodissociation of the excimer and the simultaneous fluores cence of the fragment. Fluorescence decay times of the fragment by the excimer depletion were considerably larger than those of the monomer and smaller than the dimer's. The photodissociation mechanism of the e xcimer was discussed in terms of decay times of the fragment fluoresce nce and the unexpectedly stable dimer core of 1-CNN.