THE DELAYED IONIZATION AND ATOMIC ION EMISSION OF BINARY METAL METALLOCARBOHEDRENES TI(X)M(Y)C(12) (M=ZR,NB, O-LESS-THAN-OR-EQUAL-TO-Y-LESS-THAN-OR-EQUAL-TO-4, X+Y=8)

Investigations of the photophysical character of binary metal containi ng metallocarbohedrene clusters (Met-Cars), reveal the phenomena of de layed ionization. Additionally, the onset of a channel corresponding t o delayed atomic ion emission is observed at high laser fluence, becom ing progressively more significant as the fluence is raised. The fluen ce dependence of both the delayed electron and delayed atomic ion emis sion channels at 355 and 532 nm are reported, and the Met-Car delayed ion yield estimated. At moderate fluences, the yield of the delayed el ectron emission channel leading to the Met-Car ion is found to be on t he order of 70% of the total Met-Car signal. All of the experimental f indings point to thermionic emission being the operative mechanism for the delayed ionization, while the delayed atomic ion emission is evid ently a new mechanism [B. D. May, S. F. Cartier, and A. W. Castleman, Jr., Chem. Phys. Lett. 242, 265 (1995)] which may be due to the collec tive electronic excitation of these cluster materials. (C) 1996 Americ an Institute of Physics.