Radiationless transitions in small molecules: Interstate cascading in matrix-isolated CN

Radiationless relaxation following excitation of high levels of the AΠ2 manifold in CN is shown to proceed via an interstate cascading mechanism involving the AΠ2 and X2 vibrational levels. The direct vibrational relaxation within the X2 state is shown to be slower by at least 2-3 orders of magnitude. Experimental results and a theoretical discussion of these phenomena are presented.