VIBRONIC RELAXATION DYNAMICS OF CN IN AR MATRICES AND CLUSTERS

The relaxation dynamics of CN in Ar matrices and clusters (CN-Ar-n, n approximate to 100) have been examined using time- and wavelength-reso lved fluorescence techniques. Transfer between levels of the A (2) Pi and X (2) Sigma(+) states was characterized for matrix-isolated CN. Th e transfer rate constants were consistent with a mechanism controlled by both the energy spacings between the levels, and the Franck-Condon overlaps. CN-Ar-n clusters exhibited B (2) Sigma(+) --> A (2) Pi trans fer, but evidence for subsequent A <-> X transfer was not found. Compa risons with the matrix relaxation behavior suggest that each duster co nsists of a CN radical bound to the surface of an Ar-n unit. B --> A t ransfer predissociated the clusters, yielding CN in the v(A) = 9 and 8 vibrational levels. This occurrence permitted a provisional new deter mination of the radiative lifetime for these excited vibrational level s.