DYNAMICS OF DESORPTION OF REACTION-PRODUCTS FROM REACTIONS ON LARGE CLUSTERS

The reaction of barium trimers with molecules of SF6 has been investig ated on large argon clusters (around 4000 atoms). The reaction is stro ngly exoergic (by approximately 5 eV) and leads to several reaction pr oducts; among which, the desorption of ground state BaF molecules is o bserved. The energetics of these molecules has been analysed by laser- induced fluorescence with subDoppler resolution. The rotational, vibra tional and translational energy distributions are found to be thermal, with temperatures in the range 1600-2400 K. These temperatures are lo wer than those found in a preceding analysis of chemiluminescent desor bed products but remain much higher than the temperature of the cluste r. This is interpreted by different time scales of interaction of the products with the cluster substrate: short times leading to highly int ernally excited products, long times to solvated products, with the gr ound state desorbed products appearing as intermediates in between.