Atomichron®: The atomic clock from concept to commercial product

Forman, Paul

doi:10.1109/proc.1985.13266

Cited by 48 publications

(21 citation statements)

References 15 publications

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“…We plan to use a specific isotopomer of ammonia, 15 NH 3 , as test molecule for a number of reasons: (i) The microwave spectrum of ammonia is very well studied. In fact, it was used in the first demonstration of an atomic clock by Condon and Lyons in 1948 [15] and the first demonstration of the MASER by Gordon and co-workers in 1955 [16]. The energies of the hyperfine levels of the four most common symmetric isotopomers ( 14 NH 3 , 15 NH 3 , 14 ND 3 and 15 ND 3 ) have been determined with an accuracy of better than 100 Hz [7,[17][18][19].…”

mentioning

confidence: 99%

Prospects for precision measurements on ammonia molecules in a fountain

Bethlem

Kajita

Sartakov

et al. 2008

Eur. Phys. J. Spec. Top.

114

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Abstract. The recent demonstration of cooling and manipulation techniques for molecules offer new possibilities for precision measurements in molecules. Here, we present the design of a molecular fountain based on a Stark decelerated molecular beam. In this fountain, ammonia molecules are decelerated to a few meter per second, cooled to sub microKelvin temperatures and subsequently launched. The molecules fly upwards some 30 cm before falling back under gravity, thereby passing a microwave cavity twice -as they fly up and as they fall back down. The effective interrogation time in such a Ramsey type measurement scheme includes the entire flight time between the two traversals through the driving field, which is on the order of a 1/2 second. We present numerical simulations of the trajectories through the decelerator and estimate the expected count rate. We present an evaluation of the expected stability and accuracy for the inversion transition in 15 NH3 around 22.6 GHz. The estimated frequency instability is 7 × 10 −12 τ −1/2 , with τ being the measurement time in seconds. With a careful design of the interogation zone, systematic frequency shifts are kept below 10 −14 . Besides serving as a proof-of-principle, these measurements may be used as a test of the time-variation of fundamental constants using the sensitivity of the tunneling motion to a change of the proton-electron mass ratio.

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mentioning

confidence: 99%

Prospects for precision measurements on ammonia molecules in a fountain

Bethlem

Kajita

Sartakov

et al. 2008

Eur. Phys. J. Spec. Top.

114

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“…They have also been used to verify the capability of transferring time via VLBI (Clark et al 1979). The historical development of the cesium-beam resonator is described by Forman (1985).…”

Section: Rubidium and Cesium Standardsmentioning

confidence: 99%

Very-Long-Baseline Interferometry

Thompson¹,

Moran²,

Swenson³

2017

Astronomy and Astrophysics Library

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In 1967, a new technique of interferometry was developed in which the receiving elements were separated by such a large distance that it was expedient to operate them independently with no real-time communication link. This was accomplished by recording the data on magnetic tape for later cross-correlation at a central processing station. The technique was called very-long-baseline interferometry (VLBI), a term recalling the earlier long-baseline interferometers at Jodrell Bank Observatory, in which the elements were connected by microwave links that had reached 127 km in length. The principles involved in VLBI are fundamentally the same as those involved in interferometers with connected elements. The tape recorder and its successor, disk storage, can be considered as an IF delay line of limited capacity with an unusually long propagation time, weeks instead of microseconds. The use of tape and disk recording media is motivated entirely by economics and places substantial limitations on the system. Satellite links have been demonstrated (Yen et al. 1977), but their high cost discourages their use.Tape recorders have been entirely replaced by compact disks. Data can also be transmitted to correlation facilities via the Internet in quasi real time. However, latency and throughput are significant issues, and data buffering is usually required.

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“…It seems likely that Rabi and his colleagues expected the energy transition in cesium ( 133 Cs) atoms to be the resonator for the first atomic clock [8]. Millman and Kusch (who, like Rabi, would become a Nobel Laureate in 1955), had first measured the cesium resonance frequency at Columbia in 1940, estimating the frequency of the hyperfine transition as 9191.4 megacycles.…”

Section: The First Suggestion Of Atomic Clocks and Early Researchmentioning

confidence: 99%