Metastable states’ population densities in Gd atomic beam at high‐rate evaporation by electron beam heating

Metastable states’ population densities in gadolinium atomic beams, which were produced by an axial electron beam gun, were measured by laser absorption spectroscopy at the atomic densities on the order of 1012 atoms/cm3. The following results were obtained. (1) The atomic excitation temperature derived from the metastable states distributions is considerably lower than the evaporation surface temperature. With increasing evaporation rates, the atomic excitation temperature decreased to about 500 K. (2) The densities of both ground and first metastable states increased linearly with the deposition rates as measured by a quartz crystal sensor on the beam axis, which indicates that the atomic beam is almost free from the cluster formation caused by rapid expansion into a high vacuum.