Frequency Stability in a Wall-Coated Evacuated Cell: Preliminary Results

摘要

Using a high-quality evacuated wall-coated sealed cell, first measurements on the frequency stability of the 6835 MHz 0-0 rubidium 87 hyperfine transition are reported. The intrinsic linewidth in the 24cc cell was approximately 10 Hz FWHM. A saturated absorption locked diode laser provided a stable optical pumping light source. Available equipment showed a monotonic frequency drift rate of - + 1 x 10(-12)/day. Additional experiments appear to confirm that light gas diffusion into the cell is the cause of this drift. The observed drift is closely matched by the calculated rate due to the diffusive influx of atmospheric helium through the cell wall. If such diffusion is the dominant cause of drift, improvement in frequency stability by orders of magnitude should be possible without penalties in size, weight, or cost.