A pulsed crossed supersonic molecular beam apparatus to study the dynamics of refractory atom reactions

A pulsed crossed supersonic molecular beam apparatus is described which is suitable for the determination of state-to-state reactive cross sections of ground state refractory atoms with oxidant molecules. The unique aspect of the instrument is its metal-atom beam, in which the atoms are generated by laser ablation of the corresponding solid and are entrained in neutral gases which expand supersonically at the exit of a pulsed nozzle. The peak intensities from this source can exceed the intensities obtainable with a conventional metal-oven effusive source by orders of magnitude for the more refractory elements. Other characteristics, such as a truly tunable velocity range from 600 to 3400 m s-1 associated with a velocity spread between 20 and 10% FWHM, constitute improvements over such conventional sources. Evidence of this superiority is given by comparative experiments on the reaction dynamics of carbon and aluminium. The versatility of the pulsed metal beam, which can accommodate metals, including the most refractory elements, is of great promise for future experiments in this area.