Rachel Godun

Rachel Godun is the Science Area Leader for the optical frequency metrology group within Time & Frequency at NPL. This includes optical clocks, ultrastable lasers, femtosecond frequency combs and time & frequency transfer over optical fibre links.  Rachel’s specialist area of research is the development of an optical atomic clock based on a trapped, single ion of ytterbium.  The research aims to make frequency measurements at the highest level of accuracy to support a future redefinition of the SI second and enable tests of fundamental physics.

Rachel graduated from the University of Oxford with an M.Phys. in 1997 and completed a D.Phil. in 2000, carrying out research in atom interferometry. She continued to work with ultra-cold atoms for a further 8 years in Oxford, before joining NPL in 2008.  Since then, Rachel has been working in the area of optical atomic clocks.  Rachel is a Fellow of the Institute of Physics and represents NPL on the Consultative Committee for Time and Frequency as well as its Working Group on Primary and Secondary Frequency Standards.  She is currently a vice-chair of the Scientific Committee for the European Frequency and Time Forum and also a member of its Executive Committee.

Areas of interest

• Optical clocks and frequency metrology towards a redefinition of the SI second
• Precision measurements with optical clocks to test the fundamental laws of physics
• International frequency comparisons between optical clocks in different countries
• Robust optical clocks for future time scales and optical frequency services
• Recently coordinated a European joint research project to build optical clocks with 1 × 10⁻¹⁸ uncertainty, “OC18”.

Key publications

• Analysis of atomic-clock data to constrain variations of fundamental constants
  N. Sherrill, A. O. Parsons, C. F. A. Baynham, W. Bowden, E. A. Curtis, R. Hendricks, I. R. Hill, R. Hobson, H. S. Margolis, B. I. Robertson, M. Schioppo, K. Szymaniec, A. Tofful, J. Tunesi, R. M. Godun and X. Calmet.
  New J. Phys. 25, 093012 (2023)
• Direct comparisons of European primary and secondary frequency standards via satellite techniques
  F. Riedel, A. Al-Masoudi, E. Benkler, S. Dörscher, V. Gerginov, C. Grebing, S. Häfner, N. Huntemann, B. Lipphardt, C. Lisdat, E. Peik, D. Piester, C. Sanner, C. Tamm, S. Weyers, H. Denker, L. Timmen, C. Voigt, D. Calonico, G. Cerretto, G. A. Costanzo, F. Levi, I. Sesia, J. Achkar, J. Guéna, M. Abgrall, D. Rovera, B. Chupin, C. Shi, S. Bilicki, E. Bookjans, J. Lodewyck, R. Le Targat, P. Delva, S. Bize, F. N. Baynes, C. F. A. Baynham, W. Bowden, P. Gill, R. M. Godun, I. R. Hill, R. Hobson, J. M. Jones, S. A. King, P. B. R. Nisbet-Jones, A. Rolland, S. L. Shemar, P. B. Whibberley and H. S. Margolis
  Metrologia 57, 045005 (2020)
• Absolute frequency measurement of the ²S_1/2 → ²F_7/2 optical clock transition in ¹⁷¹Yb⁺ with an uncertainty of 4 × 10⁻¹⁶ using a frequency link to international atomic time
  C. F. A. Baynham, R. M. Godun, J. M. Jones, S. A. King, P. B. R. Nisbet-Jones, F. Baynes, A. Rolland, P. E. G. Baird, K. Bongs, P. Gill and H. S. Margolis
  Journal of Modern Optics 65, 585 (2018)
• Frequency ratio of two optical clock transitions in ¹⁷¹Yb⁺ and constraints on the time variation of fundamental constants
  R. M. Godun, P. B. R. Nisbet-Jones, J. M. Jones, S. A. King, L. A. M. Johnson, H. S. Margolis, K. Szymaniec, S. N. Lea, K. Bongs, and P. Gill
  Physical Review Letters 113, 210801 (2014)

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