New Products

J. Stern
1961 Science  
New Products Rubidium frequency standard uses an optically pumped rubidium-87 cell as the basic frequency reference. Optical pumping to redistribute the atoms among the energy states of rubidium is effected by irradiating the cell with light from a rubidium-85 vapor discharge lamp excited to luminescence by a radio-frequency field supplied by a transistorized oscillator. When the cell is irradiated by microwave energy of proper frequency, the energy levels depleted by optical pumping tend to be
more » ... pumping tend to be replenished by a further redistribution of the atomic energy states. As a result, more pumping energy is absorbed. When the microwave energy is at the precisely correct frequency, the transmission of pumping light is at a minimum. This minimum is detected by a photodetector from which an error signal is derived that is used to maintain the microwave frequency. In the instrument, microwave energy is generated by a crystal oscillator at 6834 Mcy/ sec, the resonant frequency of rubidium-87, and is supplied to a resonant cavity containing the gas cell. The stabilized signal from the crystal oscillator is fed to a transistorized frequency synthesizer circuit that provides three output frequencies: 5 Mcy/sec, I Mcy/ sec, and 100 kcy/sec. Output power is 10 mw into a 50-ohm load. (Space
doi:10.1126/science.134.3473.227 fatcat:5ylobigsefdpdasgthydgth64i