We come now to consider what proved to be the culmination of efforts to perfect maser oscillators: the hydrogen maser, one of the most stable of all present-day frequency standards. Few other microwave quantum devices approach its overall frequency stability. Conceptually, the H-maser was a natural outgrowth of the continuing experimental drive to improve the spectral resolution of atomic beam resonance machines by increasing the interaction time between the atoms and the resonant field. This was to be achieved by confining the interacting atoms within a space defined by inert walls; however, few would have predicted the degree of inertness exhibited by one fluorocarbon polymer named Teflon and the extraordinary length of perturbation-free interaction time it made possible.
KeywordsAutomatic Tuning Atomic Frequency Resonant Field Hydrogen Maser Hyperfine State
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