The Br and Br2 molecular beam fluxes from graphite sources were studied mass spectrometrically at 300 to 1200K. The results showed that the transport out from the sources goes via bulk diffusion in the vicinity of the normal effusion opening. The pressure dependence of the signals showed that the Br and Br2 fluxes were not in chemical equilibrium. Dissociation was also higher than expected at equilibrium. The diffusing species was Br2 in most cases. This efficient diffusion process was in accord with the well-known facile intercalation of graphite with bromine. The method used may be developed to study further molecular details of transport processes. Sources using controlled diffusion and increased dissociation may also be used as high intensity molecular beam sources.

Transport of Bromine Out from a Graphite Molecular Beam Source: a Case of Bulk Diffusion. Holmlid, L., Sigurdsson, A.: Journal of Applied Physics, 1985, 57[4], 1102-8