Skip to main content Accessibility help
Hostname: page-component-59b7f5684b-8dvf2 Total loading time: 0.939 Render date: 2022-10-06T00:00:05.933Z Has data issue: true Feature Flags: { "shouldUseShareProductTool": true, "shouldUseHypothesis": true, "isUnsiloEnabled": true, "useRatesEcommerce": false, "displayNetworkTab": true, "displayNetworkMapGraph": true, "useSa": true } hasContentIssue true

11 - Microwave Atomic Clocks

Published online by Cambridge University Press:  01 October 2018

Dennis D. McCarthy
United States Naval Observatory
P. Kenneth Seidelmann
University of Virginia
Get access


Microwave atomic clocks introduced a new level of timekeeping accuracy. The Caesium atomic frequency standard became available in 1955, but it needed to be calibrated to provide a timescale matching Ephemeris Time. Commercial Caesium tubes made atomic clocks generally available. Caesium fountains have significantly improved the accuracy of atomic clocks. Hydrogen masers have been in use since the 1960s. Rubidium cell atomic clocks are readily available and Rubidium fountains promise to provide frequency standards with unprecedented stability. Stored ion and Mercury ion clocks are other sources of precise time and frequency. Laser-cooled microgravity atomic clocks are being developed for space missions.
Publisher: Cambridge University Press
Print publication year: 2018

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)


Arditi, M. (1958). L’influence des gaz tampons sur le déplacement de la fréquence et la largeur des raies des transitions hyperfines de l’état fondamental des atomes alcalins. Le Journal de Physique et le Radium, 19, 873.CrossRefGoogle Scholar
Arditi, M. (1982). A Caesium Beam Atomic Clock with Laser Optical Pumping, as a Potential Frequency Standard. Metrologia, 18, 5966.CrossRefGoogle Scholar
Arditi, M. & Carver, T. R. (1961). Pressure, Light, and Temperature Shifts in Optical Detection of 0–0 Hyperfine Resonance of Alkali Metals. Phys. Rev., 124, 800809.CrossRefGoogle Scholar
Arditi, M. & Carver, T. R. (1964). Hyperfine Relaxation of Optically Pumped Rb87 Atoms in Buffer Gases. Phys. Rev., 136, 643649.CrossRefGoogle Scholar
Arditi, M. & Picqué, J.-L. (1980). Construction and Preliminary Tests of a Laser Optically Pumped Cesium Jet Atomic Clock. Comptes Rendus, Série B – Sciences Physiques, 290, 461464.Google Scholar
Audoin, C. (1992). Caesium Beam Frequency Standards: Classical and Optically Pumped. Metrologia, 29, 113134.CrossRefGoogle Scholar
Audoin, C. & Guinot, B. (2001). The Measurement of Time. Cambridge: Cambridge University Press.Google Scholar
Becker, W. & Werth, G. (1983). Precise Determination of the Ground State Hyperfine Splitting of 135 Ba+. Zeitschrift für Physik A, 311, 4147.CrossRefGoogle Scholar
Berkeland, D. J., Miller, J. D., Bergquist, J. C., Itano, W. M., & Wineland, D. J. (1998). Laser-Cooled Mercury Ion Frequency Standard. Phys. Rev. Lett., 80, 20892092.CrossRefGoogle Scholar
Blatt, R. & Werth, G. (1982). Precision Determination of the Ground-State Hyperfine Splitting in 137 Ba+ Using the Ion-Storage Technique. Phys. Rev. A., 25, 14761482.CrossRefGoogle Scholar
Blaum, K., Novokov, Yu, N., & Werth, G. (2010). Penning Traps as a Versatile Tool for Precise Experiments in Fundamental Physics. Contemporary Physics, 51, 149175.CrossRefGoogle Scholar
Bollinger, J. J., Prestage, W. M., Itano, W. M., & Wineland, D. J. (1985). Laser-Cooled-Atomic Frequency Standard. Phys. Rev. Lett., 54, 10001003.CrossRefGoogle ScholarPubMed
Burt, E. A., Diener, W. A., & Tjoelker, R. L. (2008). A Compensated Multi-Pole Linear Ion Trap Mercury Frequency Standard for Ultra-Stable Timekeeping. IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 25862595.CrossRef
Carpenter, R. J., Beaty, E. C., Bender, P. L., Saito, S., & Stone, R. O. (1960). A Prototype Rubidium Vapor Frequency Standard. IRE Trans On Instrumentation, I -9, 132135.CrossRefGoogle Scholar
Church, D. A. (1969). Storage-Ring Ion Trap Derived from the Linear Quadrupole Radio-Frequency Mass Filter. J. Appl. Phys., 40, 31273134.CrossRefGoogle Scholar
Clairon, A., Ghezali, S., Santarelli, G., Laurent, Ph., Lea, S. N., Bahoura, M., Simon, E., Weyers, S., & Szymaniec, K. (1996). Preliminary Accuracy Evaluation of a Cesium Fountain Frequency Standard. In Bergquist, J. C., ed., Proceedings of the Fifth Symposium on Frequency Standards and Metrology. London: World Scientific, 4959.Google Scholar
Crampton, S. B., Greytak, T. J., Kleppner, D., Phillips, W. D., Smith, D. A., & Weinrib, A. (1979). Hyperfine Resonance of Gaseous Atomic Hydrogen at 4.2 K. Phys. Rev. Lett., 42, 10391042.CrossRefGoogle Scholar
Cutler, L. S., Flory, C. A., Giffard, R. P., & McGuire, M. D. (1986). Doppler Effects Due to Thermal Macromotion of Ions in an RF Quadrupole Trap. Appl. Phys. B, 39, 251259.CrossRefGoogle Scholar
Cutler, L. S., Giffard, R. P., & McGuire, M. D. (1985). Thermalization of 199Hg Ion Macromotion by a Light Background Gas in an RF Quadrupole Trap. Appl. Phys. B, 36, 137142.CrossRefGoogle Scholar
Davidovits, P. (1964). An Optically Pumped Rb87 Maser Oscillator. Appl. Phys. Letters, 5, 1516.CrossRefGoogle Scholar
Davidovits, P. & Novick, R. (1966). The Optically Pumped Rubidium Maser. Proceedings of the IEEE, 54, 155170.CrossRefGoogle Scholar
Du, Y., Wei, R., Dong, R., & Wang, Y. (2013) Progress of the Portable Rubidium Atomic Fountain Clock in SIOM. In Sun, J., Jiao, W., Wu, H., & Shi, C., eds., China Satellite Navigation Conference (CSNC) 2013 Proceedings. Lecture Notes in Electrical Engineering, 245. Springer.Google Scholar
Essen, L., Time for Reflection, published privately and available at; also available in Henderson, D. (2005). Essen and the National Physical Laboratory’s Atomic Clock. Metrologia, 42, S4S9.Google Scholar
Essen, L. & Parry, J. V. L. (1955). An Atomic Standard of Frequency and Time Interval: A Cæsium Resonator. Nature, 176, 280282.CrossRefGoogle Scholar
Essen, L. & Parry, J. V. L. (1957). The Caesium Resonator as a Standard of Frequency and Time. Philos. Trans. Roy. Soc. London. Ser. A, Mathematical and Physical Sciences, 250, 4569.CrossRefGoogle Scholar
Fang, F., Li, M., Lin, P., Chen, W., Liu, N., Lin, Y., Wang, P., Liu, K., Suo, R., & Li, T. (2015). NIM5 Cs Fountain Clock and Its Evaluation. Metrologia, 52, 454468.CrossRefGoogle Scholar
Fertig, C. & Gibble, K. (2000). Measurement and Cancellation of the Cold Collision Frequency Shift in an 87Rb Fountain Clock. Phys. Rev. Lett., 85, 16221625.CrossRefGoogle Scholar
Fisk, P. T. H., Sellars, M. J., Lawn, M. A., Coles, C., Mann, A. G., & Blair, D. G. (1995). Very High Q Microwave Spectroscopy on Trapped 171Yb+ Ions: Application as a Frequency Standard. IEEE Transactions on Instrumentation and Measurement, 44, 113116.CrossRefGoogle Scholar
Forman, P. (1998). Atomichron: The Atomic Clock from Concept to Commercial Product. Available at
Gerginov, V., Nemitz, N., Weyers, S., Schröder, R., Griebsch, B., & Wynands, R. (2010). Uncertainty Evaluation of the Caesium Fountain Clock PTB-CSF2. Metrologia 47, 6579.CrossRefGoogle Scholar
Goldenberg, H. M., Kleppner, D., & Ramsey, N. F. (1960). Atomic Hydrogen Maser. Phys. Rev. Lett., 5, 361362.CrossRefGoogle Scholar
Golding, W. M., Frank, A., Beard, R., White, J., Danzy, F., & Powers, E. (1994). The Double Bulb Rubidium Maser. In Proceedings of the 1994 IEEE International Frequency Control Symposium. Boston, MA: Institute of Electrical and Electronics Engineers,724730.Google Scholar
Guena, J., Rosenbusch, P., Laurent, Ph., Abgrall, M., Rovera, D., Lours, M., Santarelli, G., Tobar, M. E., Bize, S., & Clairon, A. (2013). Demonstration of a Dual Alkali Rb/Cs Atomic Fountain Clock. arXiv:1301.0483v1 3 Jan2013.
Hess, H. F., Kochanski, G. P., Doyle, J. M., Greytak, T. J., & Kleppner, D. (1986). Spin-Polarized Hydrogen Maser. Phys. Rev. A, 34, 16021604.CrossRefGoogle ScholarPubMed
Hürlimann, M. D., Hardy, W. N., Berlinsky, A. J., & Cline, R. W. (1986). Recirculating Cryogenic Hydrogen Maser. Phys. Rev. A, 34, 16051608.CrossRefGoogle ScholarPubMed
Itano, W. M. (1991). Atomic Ion Frequency Standards. Proceedings of the IEEE, 79, 936942.CrossRefGoogle Scholar
Itano, W. M. & Wineland, D. J. (1981). Precision Measurement of the Ground-State Hyperfine Constant of 25 Mg+. Phys. Rev. A., 24, 13641373.CrossRefGoogle Scholar
Jardino, M., Desaintfuscien, M., Barillet, R., Viennet, J., Petit, P., & Audoin, C. (1981). Frequency Stability of a Mercury Ion Frequency Standard. Appl. Phys. A, 24, 107112.CrossRefGoogle Scholar
Kasevich, M., Riis, E., Chu, S., & DeVoe, R. G. (1989). RF Spectroscopy in an Atomic Fountain. Phys. Rev. Lett., 63, 612615.CrossRefGoogle Scholar
Kastler, A. (1950). Quelques suggestions concernant la production optique et la détection optique d’une inégalité de population des niveaux de quantification spatiale des atomes. Application à l’expérience de Stern et Gerlach et à la résonance magnétique. Le Journal de Physique et le Radium, 11, 255265.CrossRefGoogle Scholar
Kleppner, D., Berg, H. C., Crampton, S. B., Ramsey, N. F., Vessot, R. F. C., Peters, H. E., & Vanier, J. (1965). Hydrogen Maser Principles and Techniques. Phys. Rev., 138, A972A983.CrossRefGoogle Scholar
Kleppner, D., Goldberg, H. M., & Ramsey, N. F. (1962). Theory of the Hydrogen Maser. Phys. Rev., 126, 603615.CrossRefGoogle Scholar
Li, R. & Gibble, K. (2011). Comment on “Accurate Rubidium Atomic Fountain Frequency Standard.” Metrology 48, 446447.CrossRefGoogle Scholar
Lombardi, M. A., Heavner, T. P., & Jefferts, S. R. (2007). NIST Primary Frequency Standards and the Realization of the SI Second. Measure, 2, 7489.Google Scholar
Ludlow, A. D., Boyd, M. M., Ye, J., Peik, E., & Schmidt, P. O. (2015). Optical Atomic Clocks. Rev. Mod. Phys., 87, 637701.CrossRefGoogle Scholar
Lyons, H. (1949). The Atomic Clock. Instruments, 22, 133135.Google Scholar
Major, F. G. & Werth, G. (1973). High-Resolution Magnetic Hyperfine Resonance in Harmonically Bound Ground State 199Hg Ions. Phys. Rev. Lett. 30, 11551158.CrossRefGoogle Scholar
Markowitz, W., Hall, R. G., Essen, L., & Perry, J. V. L. (1958). Frequency of Cesium in Terms of Ephemeris Time. Phys. Rev. Lett. 1, 105107.CrossRefGoogle Scholar
McCoubrey, A. O. (1996). History of Atomic Frequency Standards: A Trip through 20th Century Physics. In Proceedings of the 1996 IEEE International Frequency Control Symposium. IEEE, 12251241.
Millman, S. & Kusch, P. (1940). On the Radiofrequency Spectra of Sodium, Rubidium and Caesium. Phys. Rev., 58, 438445.CrossRefGoogle Scholar
Münch, A., Berkler, M., Gerz, Ch., Wilsdorf, D., & Werth, G. (1987). Precise Ground-State Hyperfine Splitting in 173Yb II. Phys. Rev. A., 35, 41474150.CrossRefGoogle ScholarPubMed
Ovchinnikov, Y. & Marra, G. (2011). Accurate Rubidium Atomic Fountain Frequency Standard. Metrology, 48, 87100.CrossRefGoogle Scholar
Ovchinnikov, Y. B., Szymaniec, K., & Edris, S. (2015). Measurement of Rubidium Ground-State Hyperfine Transition Frequency Using Atomic Fountains. Metrology, 52, 595599.CrossRefGoogle Scholar
Packard, M. E. & Swartz, B. E. (1962). The Optically Pumped Rubidium Vapor Frequency Standard. IREE Trans. on Instrumentation, I -11, 215223.CrossRefGoogle Scholar
Peil, S., Hanssen, J., Swanson, T. B., Taylor, J., & Ekstrom, C. R. (2016). The USNO Rubidium Fountains. 8th Symposium on Frequency Standards and Metrology 2015, Journal of Physics Conference Series, 721, 012004.Google Scholar
Peterman, P., Gibble, K., Laurent, Ph., & Salomon, C. (2016). Microwave Lensing Frequency Shift of the PHARAO Laser Cooled Microgravity Atomic Clock Metrologia, 53, 899907.CrossRefGoogle Scholar
Picqué, J.-L. (1977). Hyperfine Optical Pumping of a Cesium Atomic Beam, and Applications. Metrologia, 13, 115119.CrossRefGoogle Scholar
Prestage, J. D., Dick, G. J., & Maleki, L. (1989). New Ion Trap for Frequency Standard Applications. J. Appl. Phys., 66, 10131017.CrossRefGoogle Scholar
Prestage, J. D., Tjoelker, R. J., Dick, G. J., & Maleki, L. (1995). Progress Report on the Improved Linear Ion Trap Physics Package. Proc. 49th Ann. Symp. Freq. Control Symposium, 8285.
Prestage, J. D., Tjoelker, R. J., & Maleki, L. (2001). Recent Developments in Microwave Ion Clocks. In Luiten, A. N., ed., Topics in Applied Physics, Frequency Measurement and Control, 79. Heidelberg: Springer-Verlag, 195211.CrossRefGoogle Scholar
Rabi, I. I., Millman, S., Kush, P., & Zacharias, J. R. (1939). The Molecular Beam Resonance Method for Measuring Nuclear Magnetic Moments, The Magnetic Moments of 3Li6, 3Li7 and 9F19. Phys. Rev., 55, 526535.CrossRefGoogle Scholar
Ramsey, N. F. (1949). A New Molecular Beam Resonance Method. Phys. Rev., 76, 996.CrossRefGoogle Scholar
Ramsey, N. F. (1950). A Molecular Beam Resonance Method with Separated Oscillating Fields. Phys. Rev., 78, 695699.CrossRefGoogle Scholar
Ramsey, N. F. (1983). History of Atomic Clocks. Journal of Research of the National Bureau of Standards, 88, 301320.CrossRefGoogle Scholar
Ramsey, N. F. (1993). I. I. Rabi 1898–1988, Biographical Memoir. Washington, DC:National Academy of Sciences.Google Scholar
Ramsey, N. F. (2005). History of Early Atomic Clocks. Metrologia, 42, S1S3.CrossRefGoogle Scholar
Sherwood, J., Lyons, H., McCracken, R., & Kusch, P. (1952). High Frequency Lines in the hfs Spectrum of Cesium. Bulletin of the American Physical Society, 27, 43.Google Scholar
Song, H-j., Dong, S-w., & Wang, Z-m. (2016). An Analysis of NTSC’s Timekeeping Hydrogen Masers. Chinese Astronomy and Astrophysics, 40, 569577.Google Scholar
Sullivan, D. B., Bergquist, J. C., Bollinger, J. J., Drullinger, R. E., Itano, W. M., Jefferts, S. R., Lee, W. D., Meekhof, D., Parker, T. E., Walls, F. L., & Wineland, D. J. (2001). Primary Atomic Frequency Standards at NIST. Journal of Research of the National Institute of Standards and Technology, 106, 4763.CrossRefGoogle ScholarPubMed
Tjoelker, R. L., Bricker, C., Diener, W., Hamell, R. L., Kirk, A., Kuhnle, P., Maleki, L., Prestage, J. D., Santiago, D., Seidel, D., Stowers, D. A., Sydnor, R. L., Tucker, T. (1996). A Mercury Ion Frequency Standard Engineering Prototype for the NASA Deep Space Network. Proceedings of the 1996 IEEE/EIA International Frequency Control Symposium and Exhibition, 10731081.CrossRef
Tjoelker, R. L., Chung, S., Diener, W., Kirk, A., Maleki, L., Prestage, J. D., & Young, B, (2000). Nitrogen Buffer Gas Experiments in Mercury Trapped Ion Frequency Standards. Proceedings of the 2000 IEEE/EIA International Frequency Control Symposium and Exhibition, 668671.CrossRef
Vessot, R. F. C. (2005). The Atomic Hydrogen Maser Oscillator. Metrologia, 42, S80S89.CrossRefGoogle Scholar
Vessot, R. F. C., Levine, M. W., & Mattison, E. M. (1977). Comparison of Theoretical and Observed Maser Stability Limitation Due to Thermal Noise and the Prospect of Improvement by Low Temperature Operation. Proceedings of the 9th Annual Precise Time and Time Interval (PTTI) Applications and Planning Meeting (NASA, Goddard Space Flight Center 29 November–1 December 1977), 549.
Vessot, R. F. C., Mattison, E. M., & Blomberg, E. L. (1979). Research with a Cold Atomic Hydrogen Maser. In Annual Frequency Control Symposium, May 30–June 1, 1979, Proceedings. Washington, DC: Electronic Industries Association, 511514.Google Scholar
Walsworth, R. L., Silvera, I. F., Godfried, H. P., Agosta, C. C., Vessot, R. F. C., & Mattison, E. M. (1986). Hydrogen Maser at Temperatures below 1 K. Phys. Rev. A, 34, 2550.CrossRefGoogle ScholarPubMed
Wineland, D. J. & Itano, W. M. (1979). Laser Cooling of Atoms. Phys. Rev. A., 20, 15211540.CrossRefGoogle Scholar

Save book to Kindle

To save this book to your Kindle, first ensure is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.

Note you can select to save to either the or variations. ‘’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.

Find out more about the Kindle Personal Document Service.

Available formats

Save book to Dropbox

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.

Available formats

Save book to Google Drive

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.

Available formats