Hydrogen Maser Wall Shift Experiments and Determination of the Unperturbed Hyperfine Frequency of the Ground State of the Hydrogen Atom

The principal accuracy limitation of a hydrogen maser is the uncertainty in the determination of the hydrogen maser wail shift. In this paper, we describe in detail the experiments on hydrogen maser wall shift and introduce briefly works on hydrogen masers in the Shanghai Bureau of Metrology. In experiments, we changed five different size storage bulbs by. turns. These bulbs were all coated in the same way with a locally made F4 coating. Results of the experiments are K(40°C) = -293 ± 17 mHzcm and a(40°C) = (-17 ± 2) × 10-30C-1. The unperturbed hyperfine frequency of the ground state of the hydrogen atomf0-0 was obtained by comparing five hydrogen masers to Loran C navigation system signals for one month. The average value in respect to TAI isf0-0 = 1420 405 751.768 ± 0.002 Hz. This value is closely in agreement with values of f0-0, which have been published by other authors since 1970.