Factors determining dissociation fractions in atomic beams generated by ‘‘straight-through’’ microwave discharge sources

We have studied the parameters affecting the degree of dissociation in atomic beams produced by a source consisting of a quartz tube with an exit slit downstream from a microwave discharge, which is maintained by means of an Evenson cavity. These parameters include the effects of catalysts, discharge tube diameter, slit width, cavity-slit distance, discharge power, and tube material in producing atomic beams of hydrogen, oxygen, nitrogen, and the halogens. The achievable degree of dissociation is found to be quite sensitive to all those parameters except discharge power and tube material. Optimal values are presented.