In this review article we describe some recent results obtained in our laboratory. The successful
combination of crossed molecular beam techniques and various laser excitation schemes has been used to
study chemiluminescent reactions of ground and excited electronic states of barium with free molecules
and molecular clusters. Studies include the identification of reaction products in cases where many
chemiluminescent reaction channels are opened. The case of Ba(6sp1P1,6s5d1D2,6s5d3Dj) reacting with
H20, methanol, ethanol, propanol-1, propanol-2, methyl-2, propanol-2, butanol-l, allyl alcohol, dimethyl
ether, diethyl ether and diallyl ether is examined. A reaction mechanism is proposed which accounts
for all these reactions. Studies reported in this review also include the unravelling of reaction dynamics
where various forms of energy are mixed (electronic and kinetic energy). This is shown in studies of
Ba(1D2and1P1)+O2 reactions. Finally the role of molecular clusters as reactant is examined. Evidence
is provided that clusters of N20, H20 and CO2, in collision with Ba(1S0and1P1)+O2, do not lead efficiently to
both reactive and non reactive luminescent exit channels.
