REACTION BETWEEN (N2O, AR) BINARY CLUSTERS AND BARIUM ATOMS

Chemiluminescence is observed when barium atoms collide with N2O(Ar)n clusters in a crossed-beam experiment (200 < n < 2000 atoms). It is due to radiative decay of electronically excited BaO molecules. Evolution of the shape of the chemiluminescence spectra with cluster size n suggests two different reaction products: one is similar to that observed in the gas phase ("hot" BaO*), and the other to that observed in matrices ("cold" BaO*). The formation of the "matrix-like" product is of increasing importance as the size of the cluster increases. The following mechanism is proposed: barium atoms are captured with a large cross section by the cluster, they migrate on or in the cluster to find the N2O molecule and react. Because N2O molecules may be located at the surface, or inside the cluster, the BaO molecules give different emission spectra.