Rb O-O hyperfine transition in evacuated wall-coated cell at melting temperature

Using an evacuated wall-coated cell, a high-resolution measurement was made of the behavior of the Rb87O-O hyperfine transition frequency near the melting temperature of the coating. Several features attributed to phase changes in the coating were evident. Notable were a phase transition from a super-cooled state and three regions of zero or small temperature coefficient of hyperfine frequency. The hyperfine resonance persists above the melting point of the coating. Data were analyzed in terms of an adsorption model for the Rb-wall interaction. The 10 Hz FWHM intrinsic hyperfine line width provided evidence for a high-quality wall coating.