Ion Frequency Standards

The following publications have been approved for release by NIST. The downloadable versions may differ slightly from the final, published versions.

1. K. Beloy, M. I. Bodine, T. Bothwell, S. M. Brewer, S. L. Bromley, J.-S. Chen, J. D. Deschênes, S. A. Diddams, R. J. Fasano, T. M. Fortier, Y. S. Hassan, D. B. Hume, D. Kedar, C. J. Kennedy, I. H. Khader, A. Koepke, D. R. Leibrandt, H. Leopardi, A. D. Ludlow, W. F. McGrew, W. R. Milner, N. R. Newbury, D. Nicolodi, E. Oelker, T. E. Parker, J. M. Robinson, S. Romisch, S. A. Schäffer, J. A. Sherman, L. C. Sinclair, L. Sonderhouse, W. C. Swann, J. Yao, J. Ye and X. Zhang, "Frequency ratio measurements at 18-digit accuracy using an optical clock network", Nature 591, 564 (2021).
2. H. Leopardi, K. Beloy, T. Bothwell, S. M. Brewer, S. L. Bromley, J.-S. Chen, S. A. Diddams, R. J. Fasano, Y. S. Hassan, D. B. Hume, D. Kedar, C. J. Kennedy, D. R. Leibrandt, A. D. Ludlow, W. F. McGrew, W. R. Milner, D. Nicolodi, E. Oelker, T. E. Parker, J. M. Robinson, S. Romisch, J. A. Sherman, L. Sonderhouse, J. Yao, J. Ye, X. Zhang, and T. M. Fortier, "Measurement of the ²⁷Al⁺ and ⁸⁷Sr absolute optical frequencies", Metrologia 58, 015017 (2021).
3. M. I. Bodine, J. D. Deschênes, I. H. Khader, W. C. Swann, H. Leopardi, K. Beloy, T. Bothwell, S. M. Brewer, S. L. Bromley, J. S. Chen, S. A. Diddams, R. J. Fasano, T. M. Fortier, Y. S. Hassan, D. B. Hume, D. Kedar, C. J. Kennedy, A. Koepke, D. R. Leibrandt, A. D. Ludlow, W. F. McGrew, W. R. Milner, D. Nicolodi, E. Oelker, T. E. Parker, J. M. Robinson, S. Romisch, S. A. Schäffer, J. A. Sherman, L. Sonderhouse, J. Yao, J. Ye, X. Zhang, N. R. Newbury, and L. C. Sinclair, "Optical atomic clock comparison through turbulent air", Phys. Rev. Res. 2, 033395 (2020).
4. Ethan R. Clements, May E. Kim, Kaifeng Cui, Aaron M. Hankin, Samuel M. Brewer, Jose Valencia, Jwo-Sy Chen, Chin-Wen Chou, David R. Leibrandt, and David B. Hume, "Lifetime-Limited Interrogation of Two Independent ²⁷Al⁺ Optical Clocks Using Correlation Spectroscopy" Phys. Rev. Lett. 125, 243602 (2020).
5. Y. Lin, D. R. Leibrandt, D. G. Leibfried, and C. W. Chou, "Quantum entanglement between an atom and a molecule", Nature 581, 273 (2020).
6. C. W. Chou, A. L. Collopy, C. Kurz, Y. Lin, M. E. Harding, P. N. Plessow, T. Fortier, S. Diddams, D. Leibfried, and D. R. Leibrandt, "Frequency-comb spectroscopy on pure quantum states of a single molecular ion", Science 367, 1458 (2020).
7. Samuel M. Brewer, Jwo-Sy Chen, Aaron M. Hankin, Ethan R. Clements, Chin-Wen Chou, Kyle Beloy, William F. McGrew, Xiaogang Zhang, Robert J. Fasano, Daniele Nicolodi, Holly Leopardi, Tara M. Fortier, Scott A. Diddams, Andrew D. Ludlow, David J. Wineland, David R. Leibrandt and  David B. Hume, "Measurements of ²⁷Al⁺ and ²⁵Mg⁺ magnetic constants for improved ion clock accuracy" Phys. Rev. A 100, 033419 (2019).
8. Aaron M. Hankin, Ethan R. Clements,  Yao Huang, Samuel M. Brewer, Jwo-Sy Chen,  Chin-Wen Chou,  David B. Hume and David R. Leibrandt, "Systematic uncertainty due to background-gas collisions in trapped-ion optical clocks", Phys. Rev. A 100, 033419 (2019).
9. Samuel M. Brewer, Jwo-Sy Chen, Aaron M. Hankin, Ethan R. Clements, Chin-Wen Chou, David J. Wineland, David B. Hume and David R. Leibrandt, "An Al⁺ quantum-logic clock with systematic uncertainty below 10^-18", Phys. Rev. Lett. 123, 033201 (2019).
10. Jwo-Sy Chen, "Ticking near the Zero-Point Energy: towards 1 x 10^-18 Accuracy in AI⁺ Optical Clocks", Ph.D. Thesis, Department of Physics, University of Colorado, Boulder, 2017. PDF file
11. Chin-Wen Chou, Christoph Kurz, David B. Hume, Philipp N. Plessow, David R. Leibrandt, Dietrich G. Leibfried, "Preparation and coherent manipulation of pure quantum states of a single molecular ion", Nature, 545, 203 (2017).
12. Kyle P. Beloy, David R. Leibrandt, Wayne M. Itano, "Hyperfine-mediated electric quadrupole shifts in Al+ and In+ ion clocks", Phys. Rev. A, 95, 043405 (2017).
13. David R. Leibrandt, Samuel M. Brewer, Jwo-Sy Chen, Aaron M. Hankin, David B. Hume, David J. Wineland, Chin-Wen Chou, "Trapped-ion optical atomic clocks at the quantum limits",  Proceedings of the 48th Annual Precise Time and Time Interval Systems and Applications Meeting (2017).
14. Jwo-Sy Chen, Samuel M. Brewer, Chin-Wen Chou, David J. Wineland, David R. Leibrandt, and David B. Hume, "Sympathetic Ground State Cooling and Time-Dilation Shifts in an ²⁷Al⁺ Optical Clock," Phys. Rev. Lett. 118, 053002 (2017).

15. D. B. Hume and D. R. Leibrandt, "Probing beyond the laser coherence time in optical clock comparisons", Phys. Rev. A 93, 032138 (2016).

16. Shon Cook, Till Rosenband, and David R. Leibrandt, "Laser-Frequency Stabilization Based on Steady-State Spectral-Hole Burning in Eu3+∶Y2SiO5", Phys. Rev. Lett. 114, 253902 (2015).

17. D. J. Wineland, "The evolution of the Frequency Standards and Metrology symposium and its physics", Proc. 2015 Symp. Freq. Stds. Metrology 723 (2015).

18. D.R. Leibrandt, M.J. Thorpe, C.W. Chou, T.M. Fortier, S.A. Diddams, and T. Rosenband, "Absolute and relative stability of an optical frequency reference based on spectral hole burning in Eu3+:Y2SiO5," Phys. Rev. Lett. 111, 237402 (2013)

19. M. Thorpe, D. Leibrandt, and T. Rosenband, "Shifts of optical frequency references based on spectral hole burning in Eu3+:Y2SiO5," New J. Phys. 15, 12 (2013). 

20. D. Leibrandt, J. Bergquist, and T. Rosenband, "A cavity-stabilized laser with acceleration sensitivity below 10^{^-12}/g^{^-1}," Phys. Rev. A 87, 023829 (2013).

21. D.B. Hume, C.W. Chou, D.R. Leibrandt, M.J. Thorpe, D.J. Wineland, and T. Rosenband, "Trapped-Ion State Detection through Coherent Motion," Phys. Rev. Lett. 107, 243902 (2011).

22. M.J. Thorpe, L. Rippe, T.M. Fortier, M.S. Kirchner, and T. Rosenband, "Frequency-stabilization to 6x10^{^-16} via spectral-hole burning," Nat. Photonics 10, 1038 (2011).

23. T. Rosenband, "Numerical test of few-qubit clock protocols," Proc. 2011 ICOLS Conf. 23 (2011).

24. C. Chou, D.B. Hume, M.J. Thorpe, D.J. Wineland, and T. Rosenband, "Quantum coherence between two atoms beyond Q=10¹⁵," Phys. Rev. Lett. 106, 160801 (2011).

25. D. Leibrandt, M. Thorpe, M. Notcutt, R.E. Drullinger, T. Rosenband, and J.C.Bergquist, "Spherical Reference Cavities for Frequency Stabilization of Lasers in Non-Laboratory Environments," Opt. Exp. 19, 3471 (2011).

26. C.W. Chou, D. Hume, T. Rosenband, and D.J. Wineland, "Optical Clocks and Relativity," Science 329, 1630 (2010).

27. M.J. Thorpe, D. Leibrandt, T. Fortier, and T. Rosenband, "Measurement and real-time cancellation of vibration-induced phase noise in a cavity-stabilized laser," Opt. Express 18, 18744 (2010).

28. C.W Chou, D. Hume, J.C.J. Koelemeij, D.J. Wineland, and T. Rosenband, "Frequency Comparison of Two High-Accuracy Al+ Optical Clocks," Phys. Rev. Lett. 104, 070802 (2010).

29. D. Hume, C.W. Chou, T. Rosenband, and D.J. Wineland, "Preparation of Dicke states in an ion chain," Phys. Rev. A. 80, 052302 (2009).

30. W.M. Itano, J.C. Bergquist, T. Rosenband, D.J. Wineland, D. Hume, C.W. Chou, S.R. Jefferts, T.P. Heavner, T.E. Parker, S.A. Diddams, and T. Fortier, "Frequency Measurements of Al+ and Hg+ Optical Standards," Proc. 2009 ICOLS Conf. 117 (2009).

31. T. Rosenband, D.B. Hume, C.W. Chou, J.C. Koelemeij, A. Brusch, S. Bickman, T.M. Fortier, J.E. Stalnaker, S.A. Diddams, N.R. Newbury, W.C. Swann, W.M. Itano, D.J. Wineland, and J.C. Bergquist, "Alpha-Dot or Not: Comparison of Two Single Atom Optical Clocks," Proc. 2008 Symp. Freq. Stds. Metrology 20 (2008).

32. L. Lorini, N. Ashby, A. Brusch, S. Diddams, R. Drullinger, E. Eason, T.Fortier, P. Hastings, T. Heavner, D. Hume, W. Itano, S. Jefferts, N. Newbury, T. Parker, T. Rosenband, J. Stalnaker, W. Swann, D. Wineland, and J. Bergquist, "Recent atomic clock comparisons at NIST," Eur. Phys. J. Special Topics 163, 19-35 (2008), PDF file

33. W.M. Itano, T. Rosenband, D.B. Hume, P.O. Schmidt, C.W. Chou, A. Brusch, L. Lorini, W.H. Oskay, R.E. Drullinger, S. Bickman, T.M. Fortier, J.E. Stalnaker, S.A. Diddams, W.C. Swann, N.R. Newbury, D.J. Wineland, and J.C. Bergquist, "Ratio of the Al⁺ and Hg⁺ Optical Clock Frequencies to 17 Decimal Places," Proc. International Symposium on the Foundations of Quantum Mechanics in the Light of New Technology (World Scientific, in press).

34. T. Rosenband, D. B. Hume, P. O. Schmidt, C. W. Chou, A. Brusch, L. Lorini, W. H. Oskay, R. E. Drullinger, T. M. Fortier, J. E. Stalnaker, S. A. Diddams, W. C. Swann, N. R. Newbury, W. M. Itano, D. J. Wineland, and J. C. Bergquist, "Frequency ratio of Al⁺ and Hg⁺ single-ion optical clocks; Metrology at the 17th decimal place," Science 319, 1808 - 1812 (2008).

35. T. Rosenband, D. B. Hume, A. Brusch, L. Lorini, P. O. Schmidt, T. M. Fortier, J. E. Stalnaker, S. A. Diddams, N. R. Newbury, W. C. Swann, W. H. Oskay, W. M. Itano, D. J. Wineland, and J. C. Bergquist, "Frequency comparison of Al⁺ and Hg⁺ optical standards," in Laser Spectroscopy, Proceedings of the 18th International Conference (ICOLS 2007), edited by L. Hollberg, J. Bergquist, and M. Kasevich (World Scientific, Singapore 2008) p. 297 - 302.

36. W.M. Itano, J.C. Bergquist, A. Brusch, S.A. Diddams, T.M. Fortier, T.P. Heavner, L. Hollberg, D.B. Hume, S.R. Jefferts, L. Lorini, T.E. Parker, T. Rosenband, and J.E. Stalnaker "Optical frequency standards based on mercury and aluminum ions," Proc. SPIE 6673, 667301-1 - 667303-11 (2007).

37. D. B. Hume, T. Rosenband, and D. J. Wineland, "High-fidelity adaptive qubit detection through repetitive quantum nondemolition measurements," Phys. Rev. Lett. 99, 120502-1 - 120502-4 (2007).

38. T. Rosenband, P. O. Schmidt, D. B. Hume, W. M. Itano, T. M. Fortier, J. E. Stalnaker, K. Kim, S. A. Diddams, J. C. J. Koelemeij, J. C. Bergquist, and D. J. Wineland, "Observation of the ¹S₀ to ³P₀ clock transition in ²⁷Al⁺," Phys. Rev. Lett. 98, 220801-1 - 220801-4 (2007).

39. T. M. Fortier, N. Ashby, J. C. Bergquist, M. J. Delaney, S. A. Diddams, T. P. Heavner, L. Hollberg, W. M. Itano, S. R. Jefferts, K. Kim, F. Levi, L. Lorini, W. H. Oskay, T. E. Parker, J. Shirley, and J. E. Stalnaker, "Precision atomic spectroscopy for improved limits on variation of the fine structure constant and local position invariance," Phys. Rev. Lett. 98, 070801-1 - 070801-4 (2007).

40. T. M. Fortier, N. Ashby, J. C. Bergquist, M. J. Delaney, S. A. Diddams, T. P. Heavner, L. Hollberg, W. M. Itano, S. R. Jefferts, K. Kim, W. H. Oskay, T. E. Parker, J. Shirley, J. E. Stalnaker, F. Levi, and L. Lorini, "Improved limits of variation of the fine structure constant and violation of local position invariance," Proc. Joint Meeting IEEE Intl. Freq. Control Symp. and EFTF Conf. (2007), p. 663 - 665. PDF file

41. J. E. Stalnaker, S. A. Diddams, T. M. Fortier, K. Kim, L. Hollberg, J. C. Bergquist, W. M. Itano, M. J. Delaney, L. Lorini, W. H. Oskay, T. P. Heavner, S. R. Jefferts, F. Levi, T. E. Parker, and J. Shirley, "Optical-to-microwave frequency comparison with fractional uncertainty of 10^-15" Appl. Phys. 89, 167 - 176 (2007).

42. J. E. Stalnaker, S. A. Diddams, K. Kim, L. Hollberg, E. A. Donley, T. P. Heavner, S. R. Jefferts, F. Levi, T. E. Parker, J. C. Bergquist, W. M. Itano, M. J. Jensen, L. Lorini, W. H. Oskay, and T. M. Fortier, "Absolute optical frequency measurements with a fractional frequency uncertainty at 1 x 10^-15" Proc. 2006 IEEE Intl. Freq. Control Symp. (2006), p. 462 - 469. PDF file

43. D. J. Wineland, D. Leibfried, J. C. Bergquist, R. B. Blakestad, J. J. Bollinger, J. Britton, J. Chiaverini, R. J. Epstein, D. B. Hume, W. M. Itano, J. D. Jost, M. Knill, J. C. J. Koelemeij, C. Langer, R. Ozeri, R. Reichle, T. Rosenband, T. Schaetz, P. O. Schmidt, S. Seidelin, N. Shiga, and J. H. Wesenberg, "Trapped atomic ions and quantum information processing," in Atomic Physics 20, Proceedings of the International Conference (ICAP 2006), Innsbruck, Austria, 16-21 July 2006, edited by C. Roos, H. Haffner, and R. Blatt, AIP COnf. Proc. 869 (American Institute of Physics, 2006) p. 103 - 110.

44. T. Rosenband, W. M. Itano, P. O. Schmidt, D. B. Hume, J. C. J. Koelemeij, J. C. Bergquist, and D. J. Wineland, "Blackbody radiation shift of the ²⁷Al⁺¹S₀ to ³P₀ transition," in Proceedings of the 20th European Time and Frequency Forum, 2006, p. 289-291.

45. W.H. Oskay, S. A. Diddams, E. A. Donley, T. M. Fortier, T. P. Heavner, L. Hollberg, W.M. Itano, S. R. Jefferts, M. J. Delaney, K. Kim, F. Levi, T. E. Parker, and J.C. Bergquist, "Single-atom optical clock with high accuracy," Phys. Rev. Lett. 97, 020801-1 - 020801-4 (2006).

46. W.M. Itano, "Quadrupole moments and hyperfine constants of metastable states of Ca⁺, Sr⁺, Ba⁺, Yb⁺, Hg⁺, and Au" Phys. Rev. A 73, 022510-1 - 022510-11 (2006).

47. P. O. Schmidt, T. Rosenband, J. C. J. Koelemeij, D. B. Hume, W. M. Itano, J. C. Bergquist, and D. J. Wineland, "Spectroscopy of atomic and molecular ions using quantum logic," in Non-Neutral Plasma Physics VI, Workshop on Non-Neutral Plasmas 2006, edited by M. Drewsen, U Uggerhoj, and H. Knudsen, AIP Conf. Proc. 862 (American Institute of Physics, 2006), p. 305 - 312.

48. P. O. Schmidt, T. Rosenband, C. Langer, W. M. Itano, J. C. Bergquist, and D. J. Wineland, "Spectroscopy using quantum logic," Science 309, 749-752 (2005).

49. T. Rosenband, P. O. Schmidt, J. C. J. Koelemeij, W. M. Itano, Y. Kobayashi, T. M. Fortier, S. A. Diddams, and D. J. Wineland, "Spectroscopy of a single Al⁺ ion via coupling to Be⁺," in 2005 Digest of the LEOS Summer Topical Meetings (2005), p. 103.

50. W. H. Oskay, W. M. Itano, and J. C. Bergquist, "Measurement of the quadrupole moment in the mercury ion optical clock" in 2005 Digest of the LEOS Summer Topical Meetings (2005), p. 103.

51. W.H. Oskay, W.M. Itano, and J.C. Bergquist, "Measurement of the ¹⁹⁹Hg⁺ 5d⁹6s²²D_5/2 electric quadrupole moment and a constraint on the quadrupole shift," Phys. Rev. Lett. 94, 163001-1 - 163001-4 (2005).

52. W.H. Oskay, A. Bartels, S.A. Diddams, C.W. Oates, G. Wilpers, L. Hollberg, D.J. Wineland, W.M. Itano, C.E. Tanner, and J.C. Bergquist, "The mercury-ion optical clock: Towards a measurement of the quadrupole shift," Proc. 18th European Frequency and Time Forum, (CDROM), (2004) 4p.

53. J. Ye, J.-L. Peng, R. J. Jones, K. W. Holman, J. L. Hall, D. J. Jones, S. A. Diddams, J. Kitching, S. Bize, J. C. Bergquist, L. W. Hollberg, L. Robertsson, and L.-S. Ma, "Delivery of high-stability optical and microwave frequency standards over an optical fiber network," J. Opt. Soc. Am. 20, 1459-1467 (2003).

54. S. Bize, S. A. Diddams, U. Tanaka, C. E. Tanner, W. H. Oskay, R. E. Drullinger, T. E. Parker, T. P. Heavner, S. R. Jefferts, L. Hollberg, W. M. Itano, and J. C. Bergquist, "Testing the stability of fundamental constants with the ¹⁹⁹Hg⁺ single-ion optical clock," Phys. Rev. Lett. 90, 150802-1 - 150802-4 (2003).

55. U. Tanaka, S. Bize, C. E. Tanner, R. E. Drullinger, S. A. Diddams, L. Hollberg, W. M. Itano, D. J. Wineland, and J. C. Bergquist, "The ¹⁹⁹Hg⁺ single ion optical clock: recent progress," J. Phys. B 36, 545-551 (2003).

56. W. H. Oskay, S. Bize, S. A. Diddams, R. E. Drullinger, T. P. Heavner, L. Hollberg, W. M. Itano, S. R. Jefferts, T. E. Parker, U. Tanaka, C. E. Tanner, and J. C. Bergquist, "The mercury-ion optical clock and the search for temporal variation of fundamental constants," Proc. 2003 Joint Meeting IEEE International Frequency Control Symposium and EFTF Conference, 78-81 (2003).

57. D. J. Wineland, J. C. Bergquist, T. Rosenband, P. O. Schmidt, W. M. Itano, J. J. Bollinger, D. Leibfried, and W. H. Oskay, "Ion optical clocks and quantum information processing," Proc. 2003 Joint Meeting IEEE International Frequency Control Symposium and EFTF Conference, 68-71 (2003).

58. U. Tanaka, J. C. Bergquist, S. Bize, S. A. Diddams, R. E. Drullinger, L. Hollberg, W. M. Itano, C. E. Tanner, and D. J. Wineland, "Optical frequency standards based on the ¹⁹⁹Hg⁺ ion," IEEE Trans. Instrum. Meas. 52, 245-249 (2003).

59. L. Hollberg, S. Diddams, C. Oates, A. Curtis, S. Bize, and J. Bergquist, "Atomic clocks of the future: using the ultrafast and the ultrastable," Proceedings of the 2002 Ultrafast Phenomena Meeting, p. 170-174. PDF file

60. D. J. Wineland, J. C. Bergquist, J. J. Bollinger, R. E. Drullinger, and W. M. Itano, "Quantum computers and atomic clocks," Proceedings of the 6th Symposium on Frequency Standards and Metrology, Edited by P. Gill (World Scientific, Singapore, 2002), p. 361-368. PDF file

61. J. C. Bergquist, U. Tanaka, R. E. Drullinger, W. M. Itano, D. J. WIneland, S. A. Diddams, L. Hollberg, E. A. Curtis, C. W. Oates and Th. Udem, "A mercury-ion optical clock," Proceedings of the 6th Symposium on Frequency Standards and Metrology, Edited by P. Gill (World Scientific, Singapore, 2002), p. 99-105.

62. S. A. Diddams, Th. Udem, K. R. Vogel, L.-S. Ma, L. Robertsson, C. W. Oates, E. A. Curtis, W. M. Itano, R. E. Drullinger, D. J. Wineland, J. C. Bergquist, and L. Hollberg, "A femtosecond-laser-based optical clockwork," Proceedings of the 6th Symposium on Frequency Standards and Metrology, Edited by P. Gill (World Scientific, Singapore, 2002), p. 419-426. PDF file

63. J. C. Bergquist, S. A. Diddams, C. W. Oates, E. A. Curtis, L. Hollberg, R. E. Drullinger, W. M. Itano, D. J. Wineland, and Rh. Udem, "A single ¹⁹⁹Hg⁺ ion optical clock," in Laser Spectroscopy, Proceedings of the XV International Conference, Snowbird, Utah, 10-15 June 2001, edited by S. Chu, V. Vuletic, A. J. Kerman, and C. Chin (World Scientific, 2002) p. 106-114.

64. R. E. Drullinger, Th. Udem, S. A. Diddams, K. R. Vogel, C. W. Oates, E. A. Curtis, W. D. Lee, W. M. Itano, L. Hollberg, and J. C. Bergquist, "All optical atomic clocks based on a single mercury ion and calcium atoms," Proc. 15th European Frequency and Time Forum, Neuchatel, Switzerland, March 6-8, 2001 (Swiss Foundation for Research in Microtechnology, Neuchatel, Switzerland, 2001) p. 441-445.

65. J.C. Bergquist, S. R. Jefferts, and D. J. Wineland, "Time measurement at the millennium," Physics Today 54, 37-42 (March 2001).

66. S.A.Diddams, Th. Udem, K.R. Volgel, C.W. Oates, E.A. Curtis, W.D. Lee, W.M. Itano, R.E. Drullinger, J.C. Bergquist, and L. Hollberg, "An Optical Clock Based on a Single Trapped ¹⁹⁹Hg⁺ Ion," Science 293, 825-293 (2001).

67. J.C. Bergquist, R.J. Rafac, B.C. Young, J.A. Beall, W.M. Itano, and D.J. Wineland, "Sub-dekahertz spectroscopy of ¹⁹⁹Hg⁺," Proc. SPIE, 4269, 1-7 (2001) edited by J. L. Hall and J. Ye.

68. S.A. Diddams, Th. Udem, K.R. Vogel, C.W. Oates, E.A. Curtis, R.S. Windeler, A. Bartels, J.C. Bergquist, and L. Hollberg, "A compact femtosecond-laser-based optical clockwork," Proc. SPIE, 4269, 77-83 (2001), edited by J. L. Hall and J. Ye.

69. W.M. Itano, "External-field shifts of the ¹⁹⁹Hg⁺ optical frequency standard," J. Res. NIST. 105, 829-837 (2001). PDF file

70. L. Hollberg, C.W. Oates, E.A. Curtis, E.N. Ivanov, S.A. Diddams, Th. Udem, H.G. Robinson, J.C. Bergquist, W.M. Itano, R.E. Drullinger, and D.J. Wineland, "Optical Frequency Standards and Measurements," IEEE J. Quantum Electronics 37, 1502-1513 (2001). PDF file

71. K.R. Vogel, S.A. Diddams, C.W. Oates, E.A. Curtis, R.J. Rafac, W.M. Itano, J.C. Bergquist, R.W. Fox, W.D. Lee, J.S. Wells, and L. Hollberg, "Direct comparison between two cold-atom-based optical frequency standards using a femtosecond-laser comb," Opt. Lett. 26, 102-104 (2001). PDF file

72. D.B. Sullivan, J.C. Bergquist, R.E. Drullinger, W.M. Itano, S.R. Jefferts, W.D. Lee, D.M. Meekhof, T.E. Parker, F.L. Walls, and D.J. Wineland, "Primary Atomic Frequency Standards at NIST," NIST J. of Research 106, 47-63 (2001). PDF file

73. R.E. Drullinger, Th. Udem, S.A. Diddams, K.R. Vogel, C.W. Oates, E.A. Curtis, "All-Optical Atomic Clocks," Proc. 2001 IEEE Intl. Frequency Control (Seattle, USA) 69-75. PDF file

74. Th. Udem, S.A. Diddams, K.R. Vogel, C.W. Oates, E.A. Curtis, W.D. Lee, W.M. Itano, R.E. Drullinger, J.C. Bergquist, and L. Hollberg, "Absolute frequency measurements of the Hg⁺ and Ca optical clock transitions with a femtosecond laser," Phys. Rev. Lett. 86, 4996 (2000). PDF file

75. R.J. Rafac, B.C. Young, J.A.Beall, W.M. Itano, D.J. Wineland, and J.C. Bergquist, "Sub-dekahertz ultraviolet spectroscopy of ¹⁹⁹ Hg⁺," Phys. Rev. Lett. 85, 2462 (2000). PDF file

76. B. Frech, J.S. Wells, C.W. Oates, J. Mitchell, Y.-P. Lan, T. Kurosu, L.R. Zink, L. Hollberg, T.P. Zibrova, B.C. Young, and J.C. Bergquist, "Sub-Systems for Optical Frequency Measurements: Application to the 282-nm¹⁹⁹ Hg⁺ Transiton and the 657-nm Ca Line," IEEE Trans. Ultrasonics, Ferroelectrics, and Freq. Cont., 47, 513-517 (2000). PDF file

77. Th. Udem, S.A. Diddams, K.R. Vogel, C.W. Oates, E.A. Curtis, W.D. Lee, W.M. Itano, R.E. Drullinger, J.C. Bergquist, and L. Hollberg, "Absolute frequency measurements of the Hg⁺ and Ca optical clock transitions with a femtosecond laser," Phys. Rev. Lett. 86, 4996 (2000). PDF file

78. B. C. Young, R. J. Rafac, J. A. Beall, F. C. Cruz, W. M. Itano, D. J. Wineland, and J. C. Bergquist, "Hg⁺ optical frequency standard: Recent progress" in Laser Spectroscopy, proceedings of the XIV International Conference, edited by R. Blatt, J. Eschner, D. Leibfried, and F. Schmidt-Kaler (World Scientific, Singapore, 1999) p. 61-70. PDF file

79. B.C. Young, F.C. Cruz, W.M. Itano, and J.C. Bergquist, "Visible lasers with subhertz linewidths," Phys. Rev. Lett. 82, 3799 (1999). PDF file

80. B. C. Young, F. C. Cruz, D. J. Berkeland, R. J. Rafac, J. C. Bergquist, W. M. Itano, and D. J. Wineland, "Lasers for an optical frequency standard using trapped Hg⁺ ions," Trapped Charged Particles and Fundamental Physics, AIP Conf. Proc. 457, edited by D. H. E. Dubin and D. Schneider (American Institute of Physics, Woodbury, NY, 1999), p. 337-342. PDF file

81. B. Frech, J.S. Wells, C.W. Oates, J.B. Mitchell, L. Hollberg, Y. Lan, T. Kurosu, L.R. Zink, B.C. Young, and J.C. Bergquist, " Sub-Systems for Optical Frequency Measurements: Applications to the 282 nm¹⁹⁹ Hg⁺ Transition and the 657 nm Ca Line," Proc. Joint Mtg. 13th European Freq. and Time and 1999 IEEE Int. Freq. Cont. Symp. (Besancon, France) 630-635. PDF file

82. R.J. Rafac, B.C. Young, F.C. Cruz, J.A. Beall, J.C. Bergquist, W.M. Itano, and D.J. Wineland, "¹⁹⁹Hg⁺ Optical Frequency Standard: Progress Report," Proc. Joint Mtg. 13th European Frequency and Time Forum and 1999 IEEE Int. Freq. Cont. Symp. (Besancon, France), 676-681. PDF file

83. D.J. Berkeland, J.D. Miller, F.C. Cruz, B.C. Young, R.J. Rafac, X.-P. Huang, W.M. Itano, J.C. Bergquist, and D.J. Wineland, "High-resolution, high-accuracy spectroscopy of trapped ions," in Atomic Physics 16, proceedings of the International Conference, edited by W.E. Baylis and G.W.F. Drake, (AIP Press, 1999), pp. 29-41. PDF file

84. D. J. Berkeland, J. D. Miller, F. C. Cruz, B. C. Young, J. C. Bergquist, W. M. Itano, and D. J. Wineland, "High-accuracy microwave and optical frequency standards using laser-cooled Hg⁺ ions," Proc. 2nd Int. Symp. on Modern Problems of Laser Physics, edited by S. N. Bagayev and V. I. Denisov, Laser Physics 8, 673-678 (1998). PDF file

85. F.C. Cruz, B.C. Young, and J.C. Bergquist, "Diode-pumped Nd: FAP Laser at 1.126 ?m: A Possible Local Oscillator for a Hg⁺ Optical Frequency Standard," Appl. Opt., 37, 7801-7804 (1998). PDF file

86. D.J. Berkeland, J.C. Bergquist, W.M. Itano, J.D. Miller, B.C. Young, and D.J. Wineland, " High-Performance Trapped Hg⁺ Frequency Standards," CPEM '98 Digest (Washington DC, USA), 321-322. PDF file

87. B.C. Young, D.J. Berkeland, F.C. Cruz, J.C. Bergquist, W.M. Itano, and D.J. Wineland, "Lasers for a Trapped Hg⁺ Optical Frequency Standard," CPEM '98 Digest (Washington DC, USA), 153-154. PDF file

88. D.J. Berkeland, J.D. Miller, J.C. Bergquist, W.M. Itano, and D.J. Wineland, "High-Accuracy Frequency Standards Using Laser-Cooled Hg⁺ Ions," 1998 Intl. Freq. Cont. Symp. (Pasadena, USA), 32-36. PDF file

89. D.J. Berkeland, J.D. Miller, B.C. Young, J.C. Bergquist, W.M. Itano, and D.J. Wineland, "High-accuracy frequency standards using laser-cooled Hg⁺ ions," Methods for Ultrasensitive detection, edited by B.L. Fearey, SPIE Conf. Proc. 3270 pp. 138-146 (1998). PDF file

90. D.J. Berkeland, J.D. Miller, J.C. Bergquist, W.M. Itano, and D.J. Wineland, "Minimization of ion micromotion in a Paul trap," J. Appl. Phys. 83, 5025 (1998). PDF file

91. D.J. Berkeland, J.D. Miller, J.C. Bergquist, W.M. Itano, and D.J. Wineland, "Laser-cooled mercury ion trap frequency standard," Phys. Rev. Lett. 80, 2089 (1998). PDF file

92. D.J. Berkeland, J.D. Miller, F.C. Cruz and J.C. Bergquist, W.M. Itano, and D.J. Wineland, "High-accuracy microwave and optical frequency standards in cryogenic linear ion traps," in Proc. Workshop on the Scientific Applications of Clocks in Space, November 7-8, 1996, edited by L. Maleki, JPL Publ. 97-15 (Jet Propulsion Laboratory, 1997) pp. 133-142. PDF file

93. D.J. Berkeland, F.C. Cruz and J.C. Bergquist, "Sum-frequency generation of continuous-wave light at 194 nm," Appl. Opt. 36, 4159-4162 (1997). PDF file

94. J. H. Marquardt, F. C. Cruz, M. Stephens, C. W. Oates, L. Hollberg, J. C. Bergquist, D. F. Welch, D. Mehuys, and S. Sanders, "Grating-tuned semiconductor MOPA lasers for precision spectroscopy," in Application of tunable diode and other infrared sources for atmospheric studies and industrial process monitoring, edited by A. Fried, Proc. SPIE 2834, 34-40 (1996). PDF file

95. A. Steinbach, M. Rauner, F. C. Cruz, and J.C. Bergquist, "CW second harmonic generation with elliptical Gaussian beams," Opt. Commun. 123, 207-214 (1996). PDF file

96. M.E. Poitzsch, J.C. Bergquist, W.M. Itano, and D.J. Wineland, "Cryogenic linear ion trap for accurate spectroscopy," Rev. Sci. Instrum. 67, 129-134 (1996).

97. J.D. Miller, D.J. Berkeland, F.C. Cruz, J.C. Bergquist, W.M. Itano, and D.J. Wineland, "A cryogenic linear ion trap for ¹⁹⁹Hg⁺ frequency standards," Proc. 1996 IEEE International Frequency Control Symposium (copies available from IEEE Service Center, 445 Hoes Lane, P.O. Box 1331, Piscataway, NJ 08855-1331), pp. 1086-1088. PDF file

98. J.D. Miller, M.E. Poitzsch, F.C. Cruz, D.J. Berkeland, J.C. Bergquist, W.M. Itano, and D.J. Wineland, "A Cryogenic Linear Ion Trap for ¹⁹⁹Hg⁺ Frequency Standards," 1995 IEEE Int. Freq. Cont. Sym. (San Francisco, USA), 110-112. PDF file

99. J.J. Bollinger, J.D. Prestage, W.M. Itano, and D.J. Wineland, "Laser-Cooled-Atomic Frequency Standard," Phys. Rev. Lett. 54, 1000-1003 (1995). PDF file

100. D.J. Wineland, J.C. Bergquist, D. Berkeland, J.J. Bollinger, F.C. Cruz, W.M. Itano, B.M. Jelenkovic, B.E. King, D.M. Meekhof, J.D. Miller, C.R. Monroe, and J.N. Tan, " Application of Laser-Cooled Ions to Frequency Standards and Metrology Proc. Fifth Symp. on Frequency Standards and Metrology, Woods Hole, MA, Oct. 16-19, pp. 11-19 (1995). PDF file

101. W.M. Itano, "High-Magnetic-Field Corrections to Cesium Hyperfine Structure," Proc. Fifth Symp. on Frequency Standards and Metrology, Woods Hole, MA, Oct. 16-19, pp. 503-504 (1995). PDF file

102. J.J. Bollinger, D.J. Wineland, W.M. Itano, and D.J. Heinzen, "Spin Squeezing Applied to Frequency Standards," Proc. Fifth Symp. on Frequency Standards and Metrology, Woods Hole, MA, Oct. 16-19, pp.107-113 (1995).

103. J. N. Tan, J.J. Bollinger, and D.J. Wineland, "Minimizing time dilation in Penning trap ion clocks," Proc. Fifth Symp. on Frequency Standards and Metrology, Woods Hole, MA, Oct. 16-19, pp.427-429 (1995).

104. J.N. Tan, J.J. Bollinger, and D.J. Wineland, "Minimizing the time-dilation shift in Penning trap atomic clocks," IEEE Trans. Instrum. Meas. 44, 144-147 (1995). PDF file

105. M.E. Poitzsch, J.C. Bergquist, W.M. Itano, and D.J. Wineland, "Progress Toward a Cryogenic ¹⁹⁹Hg⁺ Ion Frequency Standard," Digest of 1994 Conference on Precision Electromagnetic Measurements (Boulder, USA) 31-32. PDF file

106. M.E. Poitzsch, J.E. Bergquist, W.M. Itano, and D.J. Wineland, "Progress on a Cryogenic Linear Trap for ¹⁹⁹Hg⁺ Ions," Proc. 1994 IEEE Int. Freq. Control Symp. (Boston, USA), 744-746.

107. W.M. Itano and N.F. Ramsey, "The Accurate Measurement of Time," Sci. Am., 269, 56-65 (1993). PDF file

108. J.C. Bergquist, W.M. Itano, and D.J. Wineland, "Laser Stabilization to a Single Ion," Proc. Varenna School (Int. School of Physics), Enrico Fermi, Italy, June 23-July 3, 1992, in Frontiers in Laser Spectroscopy, T.W. Hansch and M. Inguscio, eds. (North Holland), pp. 359-376 (1992). PDF file

109. M.C. Raizen, J.C. Bergquist, J.M. Gilligan, W.M. Itano, and D.J. Wineland, "Linear Trap for High-Accuracy Spectroscopy of Stored Ions," J. Modern Optics 39, 233-242 (1992). PDF file

110. W.M. Itano, "Atomic Ion Frequency Standards," Proc. IEEE, 79, 936-942 (1991). PDF file

111. J.C. Bergquist, W.M. Itano, D.J. Wineland, F. Diedrich, F. Elsner, and M.G. Raizen, "Single Ion Optical Frequency Standard," Proc. 45th Ann. Symp. Freq. Control (Los Angeles, USA), 524-538 (1991).

112. J.J. Bollinger, D.J. Heinzen, W.M. Itano, S.L. Gilbert, and D.J. Wineland, "A 303 MHz Frequency Standard Based on Trapped Be⁺ Ions," IEEE Trans. Instrum. Meas. 40, 126-128 (1991). PDF file

113. D.J. Wineland, W. M. Itano, J. C. Bergquist, J. J. Bollinger, D. J. Heinzen, C. H. Manney, F. L. Moore, M. G. Raizen, and C. S. Weimer, "Trapped-ion frequency standards," Proc. 1990 Precise Time and Time Interval Meeting, p. 53-60. PDF file

114. J.J. Bollinger, W.M. Itano, D.J. Heinzen, S.L. Gilbert, C.H. Manney, and M.G. Raizen, " Progress at NIST Toward Absolute Frequency Standards Using Stored Ions," IEEE Trans. Ultrason., Ferroeled., Freq. Cont. 37, 515-523 (1990). PDF file

115. J.C. Bergquist, W.M. Itano, F. Elsner, M.G. Raizen, and D.J. Wineland, "Single Ion Optical Spectroscopy," Proc. Light Induced Kinetic Effects on Atoms, Ions and Molecules Workshop (LIKE), Elba Island, Italy, May 2-5, pp. 291-299 (1990). PDF file

116. D.J. Wineland, J.C. Bergquist, W.M. Itano, F. Diedrich, and C.S. Weimer, "Frequency Standards in the Optical Spectrum," in The Hydrogen Atom G.F. Bassani, M. Inguscio, and T.W. Hansch, eds. (Springer Verlag), pp. 123-133 (1989). PDF file

117. J. A. Barnes and J. J. Bollinger, "Clocks, atomic and molecular," Encyclopedia of Physics, 2nd ed., edited by R. G. Lerner and G. L. Trigg (VCH Publ., Inc., New York, 1991), pp. 154-155. PDF file

118. J.C. Bergquist, F. Diedrich, W.M. Itano, and D.J. Wineland, "Hg⁺ Single Ion Spectroscopy," Proc. 9th Int. Laser Spectroscopy Conference, Laser Spectroscopy IX, M.S. Feld, J.E. Thomas, and A. Mooradian, eds. (Academic Press), pp. 274-277 (1989). PDF file

119. J. J. Bollinger, D. J. Wineland, W. M. Itano, J. C. Bergquist, and J. D. Prestage, "Frequency and time standards based on stored ions," Proc. 1988 Precise Time and Time Interval Meeting, p. 49-58. PDF file

120. J.C. Bergquist and S.Z. Xing, " Thermal Shifts of the Spectal Lines in the ⁴F_3/2 to ⁴I_11/2 Manifold of Nd: YAG Laser," IEEE J. Quantum Electron, 24, 1829-1832 (1988). PDF file

121. D.J. Wineland, W.M. Itano, J.C. Bergquist, J.J. Bollinger, F. Diedrich, and S.L. Gilbert, "High Accuracy Spectroscopy of Stored Ions, " Proc. 4th Symp. on Frequency Standards and Metrology, A. DeMarchi, ed. (Springer Verlag) Ancona, Italy, September 5-9, pp. 71-77 (1988). PDF file

122. J.C. Bergquist, F. Diedrich, W.M. Itano, and D.J. Wineland, "Hg⁺ Single Ion Spectroscopy," Proc. 4th Symp. of Frequency Standards and Metrology, Ancona, Italy, September 5-9, pp. 287-292 (1988). PDF file

123. J.J. Bollinger, S.L. Gilbert, W.M. Itano, and D.J. Wineland, "Frequency Standards Utilizing Penning Traps," Proc. 4th Symp. on Frequency Standards and Metrology, A. DeMarchi, ed. (Springer-Verlag) Ancona, Italy, September 5-9, pp. 319-325 (1988). PDF file

124. D.J. Wineland, W.M. Itano, J.C. Bergquist, and R.G. Hulet, "Laser Cooling Limits and Single Ion Spectroscopy," Phys. Rev. A 36, 2758-2762 (1987). PDF file

125. J.C. Bergquist, W.M. Itano, and D.J. Wineland, "Recoilless Optical Absorptions and Doppler Sidebands of a Single Trapped Ion," Phys. Rev. A 36, 428-430 (1987). PDF file

126. D.J. Wineland, "Frequency standards based on stored ions," Proc. I. E. E. E. 74, 147-150 (1987). PDF file

127. J.C. Bergquist, D.J. Wineland, W.M. Itano, H. Hemmati, H.-U. Daniel, and G. Leuchs, " Doppler-Free Two-Photon Laser Spectroscopy of HgII," Proc. 39th Ann. Symp. Frq. Control (Philadelphia, USA), 85-87 (1986). PDF file

128. J.C. Bergquist, D.J. Wineland, W.M. Itano, H. Hemmati, H.-U. Daniel, and G. Leuchs, "Energy and Radiative Lifetime of the 5d⁹6s²²D_5/2 State in HgII by Doppler-Free Two Photon Laser Spectroscopy," Phys. Rev. Lett 55, 1567-1570 (1985). PDF file

129. J.J. Bollinger, J.D. Prestage, W.M. Itano, and D.J. Wineland, "Laser-cooled-atomic frequency standard," Phys. Rev. Lett. 54, 1000-1003 (1985). PDF file

130. D.J. Wineland, "Spectroscopy of stored ions," in Precision Measurement and Fundamental Constants II, edited by B. N. Taylor and W. D. Phillips, NBS Spec. Pub. 617 (1984), p. 83-92. PDF file

131. W. M. Itano, D.J. Wineland, J. C. Bergquist, and F. L. Walls, "Progress toward a stored ion frequency standard at the National Bureau of Standards," in Precision Measurement and Fundamental Constants II, edited by B. N. Taylor and W. D. Phillips, NBS Spec. Pub. 617 (1984), p. 93-97. PDF file

132. H. Hemmati, J.C. Bergquist, and W.M. Itano, "Generation of Continuous-Wave 194-nm Radiation by Sum-Freauency Mixing in an External Ring Cavity," Opt. Lett, 8, 73-75 (1983). PDF file

133. D. J. Wineland, W.M. Itano, J. C. Bergquist, and H. Hemmati, "Frequency standard research using stored ions," in Laser-Cooled and Trapped Ions, Proceedings of the Workshop on Spectroscopic Applications of Slow Atomic Beams, edited by W. D.Phillips, NBS Spec. Pub. 653 (1983), p. 19-25. PDF file

134. J.J. Bollinger, W.M. Itano, and D.J. Wineland, "Laser Cooled ⁹Be⁺ Accurate Clock," Proc. 37th Ann. Symp. Freq. Control (Philadelphia, USA), 37-41 (1983). PDF file

135. W.M. Itano, D.J. Wineland, H. Hemmati, J.C. Bergquist, and J.J. Bollinger, "Time and Frequency Standards Based on Charged Particle Trapping," IEEE Trans. Nucl. Sci. 30, 1521-1523 (1983). PDF

136. D.J. Wineland, W.M. Itano, J.C. Bergquist, and F.L. Walls, "Proposed Stored ²⁰¹Hg⁺ Ions Frequency Standards," Proc. 35th Ann. Symp. Frq. Contro. (Philadelphia, USA), 602-611 (1981). PDF file

137. D.J. Wineland, J.C. Bergquist, R.E. Drullinger, H. Hemmati, W.M. Itano and F.L. Walls, "Laser Cooled, Stored Ion Experiments at NBS and Possible Applications to Microwave and Optical Frequency Standards," J. Phys. Colloque C8 , 307-313 (1981). PDF file

138. W.M. Itano, L.L. Lewis, and D.J. Wineland, "Shift of ²S_1/2 Hyperfine Splittings Due to Blackbody Radiation and Its Influence on Frequency Standards," J. Phys. (Paris) Colloque C8, 283-287 (1981). PDF file

139. D.J. Wineland, "Prospects for stored ion frequency standards," Proc. 1981 Precise Time and Time Interval Meeting, p. 579-591. PDF file

140. J.C. Bergquist and D.J. Wineland, "Laser to Microwave Frequency Division Using Synchrotron Radiation II," Symp. Freq. Control (Atlantic City, USA), 494-497 (1979). PDF file

141. D.J. Wineland, "Laser-To-Microwave Frequency Division Using Synchrotron Radiation," J. Appl. Phys. 50, 2528-2532 (1979). PDF file

142. F.L. Walls, D.J. Wineland, and R.E. Drullinger, "New Possibilities for Frequency Standards Using Laser Cooling and Detection of Stored Ions," Proc 32nd Ann. Symp. Freq. Control (Atlantic City, USA), 453-459 (1978). PDF file