National Physical Laboratory

Time & Frequency Publications

Home of the nation's atomic time scale, NPL is the focus for time and frequency research in the UK.

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2013

A compact UHV package for microfabricated ion-trap arrays with direct electronic air-side access
G. Wilpers, P. See, P. Gill and A. G. Sinclair
Applied Physics B
111, 21 – 28 (2013)

How big is the proton?
H. S. Margolis
Science
339, 405 – 406 (2013)

 

2012

A monolithic array of three-dimensional ion traps fabricated with conventional semiconductor technology
G. Wilpers, P. See, P. Gill and A. G. Sinclair
Nature Nanotechnology
7, 572 – 576 (2012)

Spectroscopic applications of femtosecond optical frequency combs
H. S. Margolis
Chemical Society Reviews
41, 5174 – 5184 (2012)

Room temperature femtotesla radio-frequency atomic magnetometer
W. Chalupczak, R. M. Godun, S. Pustelny and W. Gawlik
Applied Physics Letter
s 100, 242401 (2012)

Enhancement of optically pumped spin orientation via spin-exchange collisions at low vapor density
W. Chalupczak, R. M. Godun, P. Anielski, A. Wojciechowski, S. Pustelny and W. Gawlik
Physical Review
A 85, 043402 (2012)

Automatic laser control for a 88Sr+ optical frequency standard
G. P. Barwood, P. Gill, G. Huang and H. A. Klein
Measurement Science and Technolog
y 23, 055201 (2012)

Longitudinal Zeeman slowers based on permanent magnetic dipoles
Y. B. Ovchinnikov
Optics Communications
285, 1175 – 1180 (2012)

Absolute frequency measurement of the 2S1/22F7/2 electric octupole transition in a single ion of 171Yb+ with 10-15 fractional uncertainty
S. A. King, R. M. Godun, S. A. Webster, H. S. Margolis, L. A. M. Johnson, K. Szymaniec, P. E. G. Baird and P. Gill
New Journal of Physics
14, 013045 (2012)

Dissemination of an optical frequency comb over fiber with 3 × 10–18 fractional accuracy
G. Marra, H. S. Margolis and D. J. Richardson
Optics Express
20, 1775 – 1782 (2012)

A simple, configurable, permanent magnet Zeeman slower for Sr
I. R. Hill, Y. B. Ovchinnikov, E. M. Bridge, E. A. Curtis, S. Donnellan and P. Gill
Proceedings of the 2012 European Frequency and Time Forum (EFTF 2012)
, pp. 545 – 549

The space optical clocks project: Development of high-performance transportable and breadboard optical clocks and advanced subsystems
S. Schiller, A. Gorlitz, A. Nevsky, S. Alighanbari, S. Vasilyev, C. Abou-Jaoudeh, G. Mura, T. Franzen, U. Sterr, S. Falke, Ch. Lisdat, E. Rasel, A. Kulosa, S. Bize, J. Lodewyck, G. M. Tino, N. Poli, M. Schioppo, K. Bongs, Y. Singh, P. Gill, G. Barwood, Y. Ovchinnikov, J. Stuhler, W. Kaenders, C. Braxmaier, R. Holzwarth, A. Donati, S. Lecomte, D. Calonico and F. Levi
Proceedings of the 2012 European Frequency and Time Forum (EFTF 2012)
, pp. 412 – 418

Development of a Kalman filter based GPS satellite clock time-offset prediction algorithm
J. Davis, S. Bhattarai and M. Ziebart
Proceedings of the 2012 European Frequency and Time Forum (EFTF 2012)
, pp. 152 – 156

Development of NPL Rb fountain frequency standard
Y. B. Ovchinnikov
Proceedings of the 2012 European Frequency and Time Forum (EFTF 2012)
, pp. 96 – 100

 

2011

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When should we change the definition of the second?
P. Gill
Philosophical Transactions of the Royal Society A 369, 4109 – 4130 (2011)

Reply to comment on “Accurate rubidium atomic fountain frequency standard”
Y. Ovchinnikov and G. Marra
Metrologia 48, 448 – 449 (2011)

Force-insensitive optical cavity
S. Webster and P. Gill
Optics Letters 36, 3572 – 3574 (2011)

Improved accuracy of the NPL-CsF2 primary frequency standard: evaluation of distributed cavity phase and microwave lensing frequency shifts
R. Li, K. Gibble and K. Szymaniec
Metrologia 48, 283 – 289 (2011)

Local representations of UTC in national laboratories
P. B. Whibberley, J. A. Davis and S. L. Shemar
Metrologia 48, S154 – S164 (2011)

Primary frequency standard NPL-CsF2: Optimized operation near the collisional shift cancellation point
K. Szymaniec and S. E. Park
IEEE Transactions on Instrumentation and Measurement 60, 2475 – 2481 (2011)

Near-resonance spin-noise spectroscopy
W. Chalupczak and R. M. Godun
Physical Review A 83, 032512 (2011)

Accurate rubidium atomic fountain frequency standard
Y. Ovchinnikov and G. Marra
Metrologia 48, 87 – 100 (2011)

High-resolution microwave frequency transfer over an 86-km-long optical fiber network using a mode-locked laser
G. Marra, R. Slavík, H. S. Margolis, S. N. Lea, P. Petropoulos, D. J. Richardson and P. Gill
Optics Letters 36, 511 – 513 (2011)

Development of a clock ensemble algorithm incorporating data from NPL’s caesium fountain
S. Shemar, J. Davis and P. Whibberley
Proceedings of the Precise Time and Time Interval (PTTI) Meeting, November 2011

A Kalman filter UTC(k) prediction and steering algorithm
J. Davis, S. L. Shemar and P. B. Whibberley
2011 Joint Conference of the IEEE International Frequency Control and the European Frequency and Time Forum (IFCS-EFTF 2011), pp. 779 – 784

Improved accuracy evaluation of the NPL-CsF2 primary frequency standard
R. Li, K. Gibble and K. Szymaniec
2011 Joint Conference of the IEEE International Frequency Control and the European Frequency and Time Forum (IFCS-EFTF 2011), pp. 56 – 57

 

2010

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Wide spectral range confocal microscope based on endlessly single-mode fiber
R. Hubbard, Y. B. Ovchinnikov, J. Hayes, D. J. Richardson, Y. J. Fu, S. D. Lin, P. See and A. G. Sinclair
Optics Express 18, 18811 – 18819 (2010)

Competition between the tensor light shift and nonlinear Zeeman effect
W. Chalupczak, A. Wojciechowski, S. Pustelny and W. Gawlik
Physical Review A 82, 023417 (2010)

Quantum electrodynamics: A chink in the armour?
J. Flowers
Nature 466, 195 – 196 (2010)

First accuracy evaluation of the NPL-CsF2 primary frequency standard
K. Szymaniec, S. E. Park, G. Marra and W. Chalupczak
Metrologia 47, 363 – 376 (2010)

Measurement and simulation of clock errors from resource-constrained embedded systems
M. A. Collett, C. E. Matthews, T. J. Esward and P. B. Whibberley
Measurement Science and Technology 21, 075203 (2010)

Common-path self-referencing interferometer for carrier-envelope offset frequency stabilization with enhanced noise immunity
V. Tsatourian, H. S. Margolis, G. Marra, D. T. Reid and P. Gill
Optics Letters 35, 1209 – 1211 (2010)

High-stability microwave frequency transfer by propagation of an optical frequency comb over 50 km of optical fiber
G. Marra, H. S. Margolis, S. N. Lea and P. Gill
Optics Letters 35, 1025 – 1027 (2010)

Frequency measurement of the 2S1/22D3/2 electric quadrupole transition in a single 171Yb+ ion
S. Webster, R. Godun, S. King, G. Huang, B. Walton, V. Tsatourian, H. Margolis, S. Lea and P. Gill
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control 57, 592 – 599 (2010)

Optical-radio-frequency resonances free from power broadening
W. Chalupczak, P. Josephs-Franks, S. Pustelny and W. Gawlik
Physical Review A 81, 013422 (2010) 

Optical frequency standards and clocks
H. S. Margolis
Contemporary Physics 51, 37 – 58 (2010)

Preliminary results from NPL’s clock ensemble algorithm using hydrogen masers and caesium clocks
S. Shemar, J. Davis and P. Whibberley
Proceedings of the 2010 European Frequency and Time Forum (EFTF 2010)

2009

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Metrology: Lattice clocks embrace ytterbium
H. S. Margolis
Nature Photonics 3, 557 – 558 (2009)

Frequency metrology and clocks
H. S. Margolis
Journal of Physics B 42, 154017 (2009)

Trapped ion optical clocks
H. S. Margolis
European Physical Journal Special Topics 172, 97 – 107 (2009)

Frequency measurement of the 2S1/22F7/2 electric octupole transition in a single 171Yb+ ion
K. Hosaka, S. A. Webster, A. Stannard, B. R. Walton, H. S. Margolis and P. Gill
Physical Review A 79, 033403 (2009)

Cold ions in space
F. Schmidt-Kaler, P. Wolf and P. Gill
Atom Optics and Space Physics, ed. E. Arimondo, W. Ertmer, W. P. Schleich and E. M. Rasel, Proceedings of the International School of Physics “Enrico Fermi” 168, (IOS Press, Amsterdam, 2009), pp. 351 – 374

Astrodynamical Space Test of Relativity using Optical Devices (ASTROD 1) – A class-M fundamental physics mission proposal for Cosmic Vision 2015 – 2025
T. Appourchaux, R. Burston, Y. Chen, M. Cruise, H. Dittus, B. Foulon, P. Gill, L. Gizon, H. Klein, S. Klioner, S. Kopeikin, H. Krüger, C. Lämmerzahl, A. Lobo, X. Luo, H. Margolis, W.-T. Ni, A. P. Paton, Q. Peng, A. Peters, E. Rasel, A. Rüdiger, E. Samain, H. Selig, D. Shaul, T. Sumner, S. Theil, P. Touboul, S. Turyshev, H. Wang, L. Wang, L. Wen, A. Wicht, J. Wu, X. Zhang and C. Zhao
Experimental Astronomy 23, 491–527 (2009)

Matter Wave Explorer of Gravity (MWXG)
W. Ertmer, C. Schubert, T. Wendrich, M. Gilowski, M. Zaiser, T. v. Zoest, E. Rasel, Ch. J. Bordé, A. Clairon, A. Landragin, P. Laurent, P. Lemonde, G. Santarelli, W. Schleich, F. S. Cataliotti, M. Inguscio, N. Poli, F. Sorrentino, C. Modugno, G. M. Tino, P. Gill, H. Klein, H. Margolis, S. Reynaud, C. Salomon, A. Lambrecht, E. Peik, C. Jentsch, U. Johann, A. Rathke, P. Bouyer, L. Cacciapuoti, P. De Natale, B. Christophe, B. Foulon, P. Touboul, L. Maleki, N. Yu, S. G. Turyshev, J. D. Anderson, F. Schmidt-Kaler, R. Walser, J. Vigué, M. Büchner, M.-C. Angonin, P. Delva, P. Tourrenc, R. Bingham, B. Kent, A. Wicht, L. J. Wang, K. Bongs, Hj. Dittus, C. Lämmerzahl, S. Theil, K. Sengstock, A. Peters, T. Müller, M. Arndt, L. Iess, F. Bondu, A. Brillet, E. Samain, M. L. Chiofalo, F. Levi, D. Calonico
Experimental Astronomy 23, 611–649 (2009)

Advice from the CCL on the use of unstabilized lasers as standards of wavelength: the helium-neon laser at 633 nm
J. A. Stone, J. E. Decker, P. Gill, P. Juncar, A. Lewis, G. D. Rovera and M. Viliesid
Metrologia 46, 11 – 18 (2009)

Einstein Gravity Explorer – a medium class fundamental physics mission
S. Schiller, G. Tino, P. Gill, C. Salomon, U. Sterr, E. Peik, A. Nevsky, A. Görlitz, D. Svehla, G. Ferrari, N. Poli, L. Lusanna, H. Klein, H. Margolis, P. Lemonde, P. Laurent, G. Santarelli, A. Clairon, W. Ertmer, E. Rasel, J. Müller, L. Iorio, C. Lämmerzahl, H. Dittus, E. Gill, M. Rothacher, F. Flechtner, U. Schreiber, V. Flambaum, W.-T. Ni, L. Liu, X. Chen, J. Chen, K. Gao, L. Cacciapuoti, R. Holzwarth, M. P. Heß and W. Schäfer
Experimental Astronomy 23, 573–610 (2009)

Quantum physics exploring gravity in the outer solar system: the SAGAS project
P. Wolf, Ch. J. Bordé, A. Clairon, L. Duchayne, A. Landragin, P. Lemonde, G. Santarelli, W. Ertmer, E. Rasel, F. S. Cataliotti, M. Inguscio, G. M. Tino, P. Gill, H. Klein, S. Reynaud, C. Salomon, E. Peik, O. Bertolami, P. Gil, J. Páramos, C. Jentsch, U. Johann, A. Rathke, P. Bouyer, L. Cacciapuoti, D. Izzo, P. De Natale, B. Christophe, P. Touboul, S. G. Turyshev, J. Anderson, M. E. Tobar, F. Schmidt-Kaler, J. Vigué, A. A. Madej, L. Marmet, M.-C. Angonin, P. Delva, P. Tourrenc, G. Metris, H. Müller, R. Walsworth, Z. H. Lu, L. J. Wang, K. Bongs, A. Toncelli, M. Tonelli, H. Dittus, C. Lämmerzahl, G. Galzerano, P. Laporta, J. Laskar, A. Fienga, F. Roques and K. Sengstock
Experimental Astronomy 23, 651 – 687 (2009)

Frequency measurement of the 2S1/22D3/2 electric quadrupole transition in a single 171Yb+ ion
S. Webster, R. Godun, S. King, G. Huang, B. Walton, V. Tsatourian, H. Margolis, S. Lea and P. Gill
2009 Joint Conference of the IEEE International Frequency Control and the 22nd European Frequency and Time Forum (IFCS-EFTF 2009), pp. 141 – 145

ELISA: An ultra-stable oscillator for ESA deep space antennas
S. Grop, V. Giordano, P. Y. Bourgeois, N. Bazin, Y. Kersale, M. Oxborrow, G. Marra, C. Langham, E. Rubiola and J. DeVincente
2009 Joint Conference of the IEEE International Frequency Control and the 22nd European Frequency and Time Forum (IFCS-EFTF 2009), pp. 376 – 380

A new trapped ion clock based on 201Hg+
S. Taghavi-Larigani, E. A. Burt, S. N. Lea, J. D. Prestage and R. L. Tjoelker
2009 Joint Conference of the IEEE International Frequency Control and the 22nd European Frequency and Time Forum (IFCS-EFTF 2009), pp. 774 – 777

Results of the 2008 TWSTFT calibration of seven European stations
A. Bauch, D. Piester, P. Whibberley, B. Blanzano, O. Koudelka, J. Achkar, D. Rovera, E. Kroon, E. Dierikx, L. Lorini, F. Cordara and C. Schlunegger
2009 Joint Conference of the IEEE International Frequency Control and the 22nd European Frequency and Time Forum (IFCS-EFTF 2009), pp. 1209 – 1215

Optical spectroscopy of atomic hydrogen for an improved determination of the Rydberg constant
J. L. Flowers, P. E. G. Baird, A. Evans, H. A. Klein, C. D. Langham, L. Mairiniac, H. S. Margolis and B. R. Walton
Proceedings of the 7th Symposium on Frequency Standards and Metrology, ed. L. Maleki (World Scientific, Singapore, 2009), pp. 127 – 131

Development of an optical clock based on neutral strontium atoms held in a lattice trap
E. A. Curtis, Y. B. Ovchinnikov, I. R. Hill, G. P. Barwood and P Gill
Proceedings of the 7th Symposium on Frequency Standards and Metrology, ed. L. Maleki (World Scientific, Singapore, 2009), pp. 218 – 222
An optical clock based on a single trapped 88Sr+ ion
H. S. Margolis, G. P. Barwood, G. Huang, H. A. Klein, S. N. Lea, G. Marra, V. Tsatourian, B. R. Walton and P. Gill
Proceedings of the 7th Symposium on Frequency Standards and Metrology, ed. L. Maleki (World Scientific, Singapore, 2009), pp. 241 – 249

A trapped 171Yb+ ion optical frequency standard based on the S1/2 – F7/2 transition
P. Gill, S. A. Webster, G. Huang, K. Hosaka, A. Stannard, S. N. Lea, R. M. Godun, S. A. King, B. R. Walton and H. S. Margolis
Proceedings of the 7th Symposium on Frequency Standards and Metrology, ed. L. Maleki (World Scientific, Singapore, 2009), pp. 250 – 258

Improvements to the robustness of a Ti:sapphire-based femtosecond comb at NPL
V. Tsatourian, H. S. Margolis, S. N. Lea, B. R. Walton, G. Marra, D. T. Reid and P. Gill
Proceedings of the 7th Symposium on Frequency Standards and Metrology, ed. L. Maleki (World Scientific, Singapore, 2009), pp. 291 – 295

Experiments with a new 201Hg+ ion clock
E. A. Burt, S. Taghavi-Larigani, S. N. Lea, J. D. Prestage and R. L. Tjoelker
Proceedings of the 7th Symposium on Frequency Standards and Metrology, ed. L. Maleki (World Scientific, Singapore, 2009), pp. 358 – 362

Microwave and optical frequency transfer via optical fibre
G. Marra, S. N. Lea, H. S. Margolis and P. Gill
Proceedings of the 7th Symposium on Frequency Standards and Metrology, ed. L. Maleki (World Scientific, Singapore, 2009), pp. 417 – 421

 

2008

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Ultrafast optics: Femtosecond timing distribution
P. Gill
Nature Photonics 2, 711 – 712 (2008)

Limits to time variation of fundamental constants from comparisons of atomic frequency standards
S. N. Lea
European Physical Journal Special Topics 163, 37 – 53 (2008)

A permanent Zeeman slower for Sr atomic clock
Y. B. Ovchinnikov
European Physical Journal Special Topics 163, 95 – 100 (2008)

Transportable optical frequency comb based on a mode-locked fibre laser
B. R. Walton, H. S. Margolis, V. Tsatourian and P. Gill
IET Optoelectronics 2, 182 – 187 (2008)

Thermal-noise-limited optical cavity
S. A. Webster, M. Oxborrow, S. Pugla, J. Millo and P. Gill
Physical Review A 77, 033847 (2008)

Planck, units, and modern metrology
J. L. Flowers and B. W. Petley
Annalen der Physik 17, 101 – 114 (2008)

 

2007

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Optical clocks and frequency metrology for space
H. Klein
International Journal of Modern Physics D 16, 2537 – 2540 (2007)

Prospects of operating a caesium fountain clock at zero collisional frequency shift
K. Szymaniec, W. Chalupczak, S. Weyers and R. Wynands
Applied Physics B 89, 187 – 193 (2007)

Apparent power-dependent frequency shift due to collisions in a cesium fountain
K. Szymaniec, W. Chalupczak, S. Weyers and R. Wynands
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control 54, 1721 – 1722 (2007)

Limits to time variation of fundamental constants from comparisons of atomic frequency standards
S. N. Lea
Reports on Progress in Physics 70, 1473 – 1524 (2007)

Zero-point cooling and heating-rate measurements of a single 88Sr+ ion
V. Letchumanan, G. Wilpers, M. Brownnutt, P. Gill and A. G. Sinclair
Physical Review A 75, 063425 (2007)

A Zeeman slower based on magnetic dipoles
Y. B. Ovchinnikov
Optics Communications 276, 261 – 267 (2007)

Controlled photoionization loading of 88Sr+ for precision ion-trap experiments
M. Brownnutt, V. Letchumanan, G. Wilpers, R. C. Thompson, P. Gill and A. G. Sinclair
Applied Physics B 87, 411 – 415 (2007)

Coherent networks: Moving metrology
H. S. Margolis
Nature Photonics 1, 258 – 259 (2007)

Cancellation of the collisional frequency shift in caesium fountain clocks
K. Szymaniec, W. Chalupczak, E. Tiesinga, C. J. Williams, S. Weyers and R. Wynands
Physical Review Letters 98, 153002 (2007)

The NPL Rydberg constant experiment
J. L. Flowers, P. E. G. Baird, L. Bougueroua, H. A. Klein and H. S. Margolis
IEEE Transactions on Instrumentation and Measurement 56, 331 – 335 (2007)

Observation of a sub-10-Hz 88Sr+ 2S1/22D5/2 clock transition at 674 nm
G. P. Barwood, P. Gill, G. Huang and H. A. Klein
IEEE Transactions on Instrumentation and Measurement 56, 226–229 (2007)

Optical clocks in space
S. Schiller, A. Görlitz, A. Nevsky, J. C. J. Koelemeij, A. Wicht, P. Gill, H. A. Klein, H. S. Margolis, G. Mileti, U. Sterr, F. Riehle, E. Peik, Chr. Tamm, W. Ertmer, E. Rasel, V. Klein, C. Salomon, G. M. Tino, P. Lemonde, R. Holzwarth and T. W. Hänsch
Nuclear Physics B (Proceedings Supplement) 166, 300–302 (2007)

Frequency stability and phase noise of a pair of X-band cryogenic sapphire oscillators
G. Marra, D. Henderson and M. Oxborrow
Measurement Science and Technology 18, 1224 – 1228 (2007)

Collisions in a ballistically expanding cloud of cold atoms in an atomic fountain
W. Chalupczak and K. Szymaniec
Journal of Physics B 40, 343 – 350 (2007)

Vibration insensitive optical cavity
S. A. Webster, M. Oxborrow and P. Gill
Physical Review A 75, 011801 (2007)

Measurements of statistical properties of single photons emitted by a solitary NV centre in synthetic diamond
R. Hubbard, Y. Ovchinnikov, J. Cheung, N. Fletcher, R. Murray and A. G. Sinclair
Journal of Modern Optics 54, 441 – 451 (2007)

Multiple p/2 pulse area operation of caesium fountains and the collisional frequency shift
S. Weyers, R. Wynands, K. Szymaniec and W. Chalupczak
2007 Joint Conference of the IEEE International Frequency Control Symposium and the 21st European Frequency and Time Forum (IFCS-EFTF 2007), pp. 52 – 54

Fidelity – Progress report on delivering the prototype Galileo Time Service Provider
J. Achkar, P. Tuckey, P. Ullrich, D. Valat, A. Batchelor, G. Burden, A. Bauch, D. Piester, F. Cordara, P. Tavella, J. Davis, J. Delport, R. Jones, T. Levin, G. Staton, J. Nawrocki and J.-M. Pieplu
2007 Joint Conference of the IEEE International Frequency Control Symposium and the 21st European Frequency and Time Forum (IFCS-EFTF 2007), pp. 446 – 451

Control of terahertz pulse generation by optical pulse shaping
M. R. Harper, R. A. Dudley, S. N. Lea and H. S. Margolis
Joint 32nd International Conference on Infrared and Millimeter Waves and the 15th International Conference on Terahertz Electronics (IRMMW-THz 2007), pp. 616 – 619

 

2006

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Absolute frequency measurements of the R(12) 26-0 and R(106) 28-0 transitions in 127I2 at l=543 nm
L.-S Ma, S. Picard, M. Zucco, J.-M. Chartier, L. Robertsson, P. Balling, P. Krin, J. Qian, Z. Liu, C. Shi, M. V. Alonso, G. Xu, S. L. Tan, K. Nyholm, J. Henningsen, J. Hald, W. R. C. Rowley, G. P. Barwood and R. Windeler
IEEE Transactions on Instrumentation and Measurement
55, No 3, 876–880 (2006)

Reply to the comment on “Evaluation of the primary frequency standard NPL-CsF1”
K. Szymaniec, W. Chalupczak, P. B. Whibberley, S. N. Le and D. Henderson
Metrologia 43, L18 (2006)

Monolithic microfabricated ion trap chip design for scaleable quantum processors
M. Brownnutt, G. Wilpers, P. Gill, R. C. Thompson and A. G. Sinclair
New Journal of Physics 8, 232 (2006)

Optical-clock local-oscillator stabilization scheme
V. Letchumanan, P. Gill, A. G. Sinclair and E. Riis
Journal of the Optical Society of America B 23, 714 – 717 (2006)

Coherent manipulation of atoms by copropagating laser beams
Y. B. Ovchinnikov
Physical Review A 73, 033404 (2006)

Role of atomic and light polarization in an adiabatic passage experiment
W. Chalupczak and K. Szymaniec
Journal of Physics B 39, 1081 – 1089 (2006)

Comparison between frequency standards in Europe and the USA at the 10-15 uncertainty level
A. Bauch, J. Achkar, S. Bize, D. Calonico, R. Dach, R. Hlavać, L. Lorini, T. Parker, G. Petit, D. Piester, K. Szymaniec and P. Uhrich
Metrologia 43, 109 – 120 (2006)

Trapped ion optical clocks at NPL
H. S. Margolis, G. P. Barwood, K. Hosaka, G. Huang, H. A. Klein, S. N. Lea, A. Stannard, B. R. Walton, S. A. Webster and P. Gill
Proceedings of the 20th International Conference on Atomic Physics (AIP, Melville, New York, 2006)

Towards a high-stability Rb fountain frequency standard
Y. B. Ovchinnikov, W. Chalupczak, K. Szymaniec and G. Marra
Proceedings of the 20th European Frequency and Time Forum (EFTF 2006), pp. 186 – 188

On secondary representations of the second
P. Gill and F. Riehle
Proceedings of the 20th European Frequency and Time Forum (EFTF 2006), pp. 282 – 288

An optical frequency standard based on the 2S1/22F7/2 transition in 171Yb+
S. A. Webster, A. Stannard, K. Hosaka and P. Gill
Proceedings of the 20th European Frequency and Time Forum (EFTF 2006), pp. 298 – 301

Polarisabilities and blackbody shifts in Sr+ and Yb+
S. N. Lea, S. A. Webster and G. P. Barwood
Proceedings of the 20th European Frequency and Time Forum (EFTF 2006), pp. 302 – 307

 

2005

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High precision frequency measurements of the n1 + n3 combination band of 12C2H2 in the 1.5 µm region
C. S. Edwards, G. P. Barwood, H. S. Margolis, P. Gill and W. R. C. Rowley
Journal of Molecular Spectroscopy 234, 143–148 (2005)

Development and absolute frequency measurement of a pair of 778 nm two-photon rubidium standards
C. S. Edwards, G. P. Barwood, H. S. Margolis, P. Gill and W. R. C. Rowley
Metrologia 42, 464 – 467 (2005)

High-accuracy frequency atlas of 13C2H2 in the 1.5 µm region
C. S. Edwards, H. S. Margolis, G. P. Barwood, S. N. Lea, P. Gill and W. R. C. Rowley
Applied Physics B 80, 977 – 983 (2005)

Lifetime measurement of the metastable 4d 2D5/2 state in 88Sr+ using a single trapped ion
V. Letchumanan, M. A. Wilson, P. Gill and A. G. Sinclair
Physical Review A 72, 012509 (2005)

Adiabatic passage in an open multilevel system
W. Chalupczak and K. Szymaniec
Physical Review A 71, 053410 (2005)

Optical frequency standards
P. Gill
Metrologia 42, S125 – S137 (2005)

Essen and the National Physical Laboratory’s atomic clock
D. Henderson
Metrologia 42, 54 – 59 (2005)

Optical clocks
P. Gill and H. S. Margolis
Physics World 18(5) (May 2005)

The kilogram redefinition – an interim solution
J. L. Flowers and B. W. Petley
Metrologia 42, L31 – L34 (2005)

Compact magneto-optical sources of slow atoms
Y. B. Ovchinnikov
Optics Communications 249, 473 – 481 (2005)

Cooling in an optical lattice for a caesium fountain frequency standard
W. Chalupczak, K. Szymaniec and D. Henderson
IEEE Transactions on Instrumentation and Measurement 54, 837 – 841 (2005)

An optical frequency standard based on the electric octupole transition in 171Yb+
K. Hosaka, S. A. Webster, P. J. Blythe, A. Stannard, D. Beaton, H. S. Margolis, S. N. Lea and P. Gill
IEEE Transactions on Instrumentation and Measurement 54, 759 – 762 (2005)

Evaluation of the primary frequency standard NPL-CsF1
K. Szymaniec, W. Chalupczak, P. B. Whibberley, S. N. Lea and D. Henderson
Metrologia 42, 49 – 57 (2005)

A Kalman filter clock algorithm for use in the presence of flicker frequency modulation noise
J. A. Davis, C. A. Greenhall, and P. W. Stacey
Metrologia 42, 1 – 10 (2005)

A strontium ion optical frequency standard with Hz-level uncertainty
H. S. Margolis, G. P. Barwood, G. Huang, H. A. Klein, S. N. Lea, K. Szymaniec and P. Gill
Proceedings of the 17th International Conference on Laser Spectroscopy, Scotland, 19th – 24th June 2005

 

2004

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Hertz-level measurement of the optical clock transition frequency in a single 88Sr+ ion
H. S. Margolis, G. P. Barwood, G. Huang, H. A. Klein, S. N. Lea, K. Szymaniec and P. Gill
Science 306, 1355 – 1358 (2004)

The route to atomic and quantum standards
J. L. Flowers
Science 306, 1324 – 1330 (2004)

Measurement of the electric quadrupole moment of the 4d2D5/2 level in 88Sr+
G. P. Barwood, H. S. Margolis, G. Huang, P. Gill and H. A. Klein
Physical Review Letters 93, 133001 (2004)

Optimum measurement strategies for trapped ion optical frequency standards
E. Riis and A. G. Sinclair
Journal of Physics B 37, 4719 – 4732 (2004)

Optical Ramsey spectroscopy of a single trapped 88Sr+ ion
V. Letchumanan, P. Gill, E. Riis and A. G. Sinclair
Physical Review A 70, 033419 (2004)

Subhertz-linewidth Nd:YAG laser
S. A. Webster, M. Oxborrow and P. Gill
Optics Letters 29, 1497 – 1499 (2004)

Hydrogenic systems, frequency standards and fundamental constants
J. L. Flowers, H. A. Klein and H. S. Margolis
Contemporary Physics 45, 123 – 145 (2004)

Absolute frequency measurement of a 1.5-µm acetylene standard by use of a combined frequency chain and femtosecond comb
C. S. Edwards, H. S. Margolis, G. P. Barwood, S. N. Lea, P. Gill, G. Huang and W. R. C. Rowley
Optics Letters 29, 566 – 568 (2004)

Trapped ion optical frequency standards
P. Gill, G. P. Barwood, G. Huang, H. A. Klein, P. J. Blythe, K. Hosaka, R. C. Thompson, S. A. Webster, S. N. Lea and H. S. Margolis
Physica Scripta T112, 63 – 67 (2004)

Least squares adjustment in the presence of discrepant data
M. G. Cox, A. B. Forbes, J. L. Flowers and P. M. Harris
Advanced Mathematical and Computational Tools in Metrology VI, ed. P. Ciarlini, M. G. Cox, F. Pavese and G. B. Rossi, pp. 37 – 51 (2004)

 

2003

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Trapped ion optical frequency standards
P. Gill, G. P. Barwood, H. A. Klein, G. Huang, S. A. Webster, P. J. Blythe, K. Hosaka, S. N. Lea and H. S. Margolis
Measurement Science and Technology 14, 1174 – 1186 (2003)

The characterization of regular but unevenly spaced TWSTFT data using second-difference statistics
J. A. Davis, P. M. Harris, S. L. Shemar and M. G. Cox
Metrologia 40, S312 – S318 (2003)

Least-squares analysis of time series data and its application to two-way satellite time and frequency transfer measurements
P. M. Harris, J. A. Davis, M. G. Cox and S. L. Shemar
Metrologia 40, S342 – S347 (2003)

Absolute frequency measurements of 633 nm iodine-stabilized helium-neon lasers
S. N. Lea, W. R. C. Rowley, H. S. Margolis, G. P. Barwood, G. Huang, P. Gill, J.-M. Chartier and R. S. Windeler
Metrologia 40, 84 – 88 (2003)

Absolute frequency measurement of the 674-nm 88Sr+ clock transition using a femtosecond optical frequency comb
H. S. Margolis, G. Huang, G. P. Barwood, S. N. Lea, H. A. Klein, W. R. C. Rowley, P. Gill and R. S. Windeler
Physical Review A 67, 032501 (2003)

Systematic frequency shifts of the 467 nm electric octupole transition in 171Yb+
P. J. Blythe, S. A. Webster, K. Hosaka and P. Gill
Journal of Physics B 36, 981 – 989 (2003)

Subkilohertz absolute-frequency measurement of the 467-nm electric octupole transition in 171Yb+
P. J. Blythe, S. A. Webster, H. S. Margolis, S. N. Lea, G. Huang, S.-K. Choi, W. R. C. Rowley, P. Gill and R. S. Windeler
Physical Review A 67, 020501 (2003)

Observation of the hyperfine structure of the 2S1/22D5/2 transition in 87Sr+
G. P. Barwood, K. Gao, P. Gill, G. Huang and H. A. Klein
Physical Review A 67, 013402 (2003)

Initial evaluation of the NPL caesium fountain frequency standard
K. Szymaniec, W. Chalupczak and D. Henderson
Proceedings of the Joint IEEE International Frequency Control Symposium and PDA Exhibition Jointly with the 17th European Frequency and Time Forum (IFCS-EFTF 2003), pp. 112 – 114

Commissioning and validation of a GPS common-view time transfer service at NPL
J. A. Davis, M. Stevens, P. B. Whibberley, P. W. Stacey and R. Hlavac
Proceedings of the Joint IEEE International Frequency Control Symposium and PDA Exhibition Jointly with the 17th European Frequency and Time Forum (IFCS-EFTF 2003), pp. 1025 – 1031

 

2002

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Kilohertz-resolution spectroscopy of the 2S1/22F7/2 electric octupole transition in a single 171Yb+ ion
S. A. Webster, P. Taylor, M. Roberts, G. P. Barwood and P. Gill
Physical Review A 65, 052501 (2002)

Ultracold atoms for ultrastable frequency standards
K. Szymaniec, W. Chalupczak, S. N. Lea and D. Henderson
Acta Physica Polonica B 33, 2173 – 2181 (2002)

A frequency standard using the 2S1/22F7/2 octupole transition in 171Yb+
S. A. Webster, P. Taylor, M. Roberts, G. P. Barwood, P. Blythe and P. Gill
Proceedings of the 6th Symposium on Frequency Standards and Metrology, ed. P. Gill (World Scientific, Singapore, 2002), pp. 115 – 122

Femtosecond optical frequency comb measurements of lasers stabilised to transitions in 88Sr+, 171Yb+ and I2 at NPL
S. N. Lea, H. S. Margolis, G. Huang, W. R. C. Rowley, D. Henderson, G. P. Barwood, H. A. Klein, S. A. Webster, P. Blythe, P. Gill and R. S. Windeler
Proceedings of the 6th Symposium on Frequency Standards and Metrology, ed. P. Gill (World Scientific, Singapore, 2002), pp. 144 – 151

Absolute frequency measurements with a set of transportable He-Ne/CH4 optical frequency standards and prospects for future design and applications
M. Gubin, E. Kovalchuk, E. Petrukhin, A. Shelkovnikov, D. Tyurikov, R. Gamidov, C. Erdogan, E. Sahin, R. Felder, P. Gill, S. N. Lea, G. Kramer and B. Lipphardt
Proceedings of the 6th Symposium on Frequency Standards and Metrology, ed. P. Gill (World Scientific, Singapore, 2002), pp. 453 – 460

Stability and reproducibility of an optical frequency standard based upon the 2S1/22D5/2 transition in 88Sr+
G. P. Barwood, P. Gill, G. Huang and H. A. Klein
Proceedings of the 6th Symposium on Frequency Standards and Metrology, ed. P. Gill (World Scientific, Singapore, 2002), pp. 495 – 497

Resolved sideband cooling of a single trapped strontium ion
A. G. Sinclair, M. A. Wilson, V. Letchumanan and P. Gill
Proceedings of the 6th Symposium on Frequency Standards and Metrology, ed. P. Gill (World Scientific, Singapore, 2002), pp. 498 – 500

Stability of Nd:YAG “flywheel” lasers locked to ultra-high-finesse etalons made from either ULE or mono-crystalline sapphire
M. Oxborrow, S. A. Webster and P. Gill
Proceedings of the 6th Symposium on Frequency Standards and Metrology, ed. P. Gill (World Scientific, Singapore, 2002), pp. 571 – 573

Development of a 778 nm rubidium two-photon diode laser frequency standard
C. S. Edwards, G. P. Barwood, P. Gill and W. R. C. Rowley
Proceedings of the 6th Symposium on Frequency Standards and Metrology, ed. P. Gill (World Scientific, Singapore, 2002), pp. 643 – 645

 

2001

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Atomic clocks: Raising the standards
P. Gill
Science 294, 1666 – 1668 (2001)

Progress in our knowledge of the fundamental constants of physics
J. L. Flowers and B. W. Petley
Reports on Progress in Physics 64, 1191 – 1246 (2001)

A tunable diode laser absorption spectrometer for moisture measurements in the low parts in 109 range
C. S. Edwards, G. P. Barwood, S. A. Bell, P. Gill and M. Stevens
Measurement Science and Technology 12, 1214 – 1218 (2001)

Development of optical frequency standards based upon the 2S1/22D5/2 transition in 88Sr+ and 87Sr+
G. Barwood, K. Gao, P. Gill, G. Huang and H. A. Klein
IEEE Transactions on Instrumentation and Measurement 50, 543 – 547 (2001)

Improved three-dimensional control of a single strontium ion in an endcap trap
A. G. Sinclair, M. A. Wilson and P. Gill
Optics Communications 190, 193 – 203 (2001)

A 3 THz wide optical frequency comb for the NPL methane-to-strontium frequency chain
H. S. Margolis, S. N. Lea, G. Huang and P. Gill
Proceedings of the 14th European Frequency and Time Forum (EFTF 2000), pp. 194 – 198

Laser spectroscopy of the 2S Lamb shift in hydrogenic silicon
H. A. Klein, H. S. Margolis, J. L. Flowers, K. Gaarde-Widdowson, K. Hosaka, J. D. Silver, M. R. Tarbutt, S. Ohtani and D. J. E. Knight
Hydrogen II: Physics of Simple Atomic Systems, ed. S. G. Karshenboim  (Springer Verlag, Berlin, 2001), pp. 664 – 671

Development of an ultranarrow diode laser for interrogating the 674-nm 2S1/22D5/2 clock transition in Sr+
G. P. Barwood, K. Gao, P. Gill, G. Huang and H. A. Klein
Proceedings SPIE 4269, Laser Frequency Stabilization, Standards, Measurement and Applications, p. 134 – 142 (2001)

 

2000

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International comparison of eight semiconductor lasers stabilized on 127I2 at l = 633 nm
A. Zarka, A. Abou-Zeid, D. Chagniot, J.-M. Chartier, O. Cip, J. Cliché, C. S. Edwards, F. Imkenberg, P. Jedlicka, B. Kabel, A. Lassila, J. Lazar, M. Merimaa, Y. Millerioux, H. Simonsen, M. Têtu and J.-P. Wallerand
Metrologia 37, 329 – 340 (2000)

Observation of the 2S1/22F7/2 electric octupole transition in a single 171Yb+ ion
M. Roberts, P. Taylor, G. P. Barwood, W. R. C. Rowley and P. Gill
Physical Review A 62, 020501 (2000)

Polarisation-dependent optical pumping for interrogation of a magnetic-field-independent “clock” transition in laser-cooled trapped 87Sr+
M. G. Boshier, G. P. Barwood, G. Huang and H. A. Klein
Applied Physics B 71, 51 – 56 (2000)

High precision trace humidity measurements with a fibre-coupled diode laser absorption spectrometer at atmospheric pressure
B. Schirmer, H. Venzke, A. Melling, C. S. Edwards, G. P. Barwood, P. Gill, M. Stevens, R. Benyon and P. Mackrodt
Measurement Science and Technology 11, 382 – 391 (2000)

Interferometric measurements of 127I2 reference frequencies for 1S – 2S spectroscopy in muonium, hydrogen and deuterium
S. L. Cornish, Y.-W. Liu, I. C. Lane, P. E. G. Baird, G. P. Barwood, P. Taylor and W. R. C. Rowley
Journal of the Optical Society of America B 17, 6 – 10 (2000)

Single trapped ions for optical frequency standards
H. A. Klein, G. P. Barwood, P. Gill and G. Huang
Physica Scripta T86 33 – 37 (2000)

1999

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Measurement of the 2S1/22D5/2 clock transition in a single 171Yb+ ion
M. Roberts, P. Taylor, S. V. Gateva-Kostova, R. B. M. Clarke, W. R. C. Rowley and P. Gill
Physical Review A 60, 2867 – 2872 (1999)

Measurement of the infrared 2F7/22D5/2 transition in a single 171Yb+ ion
P. Taylor, M. Roberts, G. M. Macfarlane, G. P. Barwood, W. R. C. Rowley and P. Gill
Physical Review A 60, 2829 – 2833 (1999)

Development of an IR tunable diode laser absorption spectrometer for trace humidity measurements at atmospheric pressure
C. S. Edwards, G. P. Barwood, P. Gill, B. Schirmer, H. Venzke and A. Melling
Applied Optics 38, 4699 – 4704 (1999)

International comparisons of He-Ne lasers stabilized with 127I2 at l = 633 nm (July 1993 to September 1995). Part IV: comparison of Western European lasers at l = 633 nm
H. Darnedde, W. R. C. Rowley, F. Bertinetto, Y. Millerioux, H. Haitjema, S. Wetzels, H. Pirée, E. Prieto, M. Mar Pérez, B. Vaucher, A. Chartier and J.-M. Chartier
Metrologia 36, 199 – 206 (1999)

Subkilohertz comparison of the single-ion optical clock 2S1/22D5/2 transition in two 88Sr+ traps
G. P. Barwood, G. Huang, H. A. Klein, P. Gill and R. B. M. Clarke
Physical Review A 59, R3178 – R3181 (1999)

Interferometric frequency measurements of an iodine stabilized Nd:YAG laser
G. M. MacFarlane, G. P. Barwood, W. R. C. Rowley and P. Gill
IEEE Transactions on Instrumentation and Measurement 48, 600 – 603 (1999)

Progress toward an optical frequency chain at NPL
S. N. Lea, G. M. Macfarlane, G. Huang and P. Gill
IEEE Transactions on Instrumentation and Measurement 48, 578 – 582 (1999)

A 633 nm iodine-stabilised diode-laser frequency standard
C. S. Edwards, G. P. Barwood, P. Gill and W. R. C. Rowley
Metrologia 36, 41 – 45 (1999)

Progress toward a precision measurement of the hellion magnetic moment in Bohr magnetons
J. L. Flowers, N. J. Cleaton, P. W. Josephs-Franks and B. W. Petley
IEEE Transactions on Instrumentation and Measurement 48, 209 – 211 (1999)

Development of a caesium fountain primary frequency standard at the NPL
P. B. Whibberley, D. Henderson and S. N. Lea
Proceedings of the 1999 Joint Meeting of the European Frequency and Time Forum and the IEEE International Frequency Control Symposium (IFCS-EFTF 1999), pp. 24 – 26

A study of delay instabilities within a two-way satellite time and frequency transfer Earth station
S. L. Shemar and J. A. Davis
Proceedings of the 1999 Joint Meeting of the European Frequency and Time Forum and the IEEE International Frequency Control Symposium (IFCS-EFTF 1999), pp. 208 – 212

Optical frequency synthesis in the near IR with application to trapped ion standards
S. N. Lea, G. Huang, H. S. Margolis, G. M. Macfarlane, P. Taylor and P. Gill
Proceedings of the 1999 Joint Meeting of the European Frequency and Time Forum and the IEEE International Frequency Control Symposium (IFCS-EFTF 1999), pp. 647 – 650

Ultra-stable optical frequencies for space
C. C. Hodge, H. A. Klein, D. J. E. Knight and L. Maleki
Proceedings of the 1999 Joint Meeting of the European Frequency and Time Forum and the IEEE International Frequency Control Symposium (IFCS-EFTF 1999), pp. 663 – 666

Development of an optical frequency standard based upon the 2S1/22D5/2 transition in Sr+
G. P. Barwood, P. Gill, G. Huang and H. A. Klein
Proceedings of the 1999 Joint Meeting of the European Frequency and Time Forum and the IEEE International Frequency Control Symposium (IFCS-EFTF 1999), pp. 686 – 691

Single ion spectroscopy of ytterbium
M. Roberts, P. Taylor and P. Gill
Proceedings of the 1999 Joint Meeting of the European Frequency and Time Forum and the IEEE International Frequency Control Symposium (IFCS-EFTF 1999), pp. 718 – 721

Absolute frequency measurements with a set of transportable methane optical frequency standards
O. Acef, A. Clairon, G. D. Rovera, F. Ducos, L. Hilico, G. Kramer, B. Lipphardt, A. Shelkovnikov, E. Kovalchuk, E. Petrukhin, D. Tyurikov, M. Petrovskiy, M. Gubin, R. Felder, P. Gill and S. Lea
Proceedings of the 1999 Joint Meeting of the European Frequency and Time Forum and the IEEE International Frequency Control Symposium (IFCS-EFTF 1999), pp. 742 – 745

 

1998

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A sideband-injection locked extended cavity diode laser for interrogating cold trapped strontium ions
R. B. M. Clarke, E. Riis, G. P. Barwood, P. Gill, G. Huang and H. A. Klein
Optics Communications 158, 36 – 40 (1998)

High-accuracy length metrology using multiple-stage swept-frequency interferometry with laser diodes
G. P. Barwood, P. Gill and W. R. C. Rowley
Measurement Science and Technology 9, 1036 – 1041 (1998)

Sub-kHz “clock” transition linewidths in a cold trapped 88Sr+ ion in low magnetic fields using 1092-nm polarisation switching
G. P. Barwood, P. Gill, G. Huang, H. A. Klein and W. R. C. Rowley
Optics Communications 151, 50 – 55 (1998)

Combined optical-infrared single-ion frequency standard
P. Taylor, M. Roberts, G. P. Barwood and P. Gill
Optics Letters 23, 298 – 300 (1998)

 

1997

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Investigation of the 2S1/22D5/2 clock transition in a single ytterbium ion
P. Taylor, M. Roberts, S. V. Gateva-Kostova, R. B. M. Clarke, G. P. Barwood, W. R. C. Rowley and P. Gill
Physical Review A 56, 2699 – 2704 (1997)

Observation of an electric octupole transition in a single ion
M. Roberts, P. Taylor, G. P. Barwood, P. Gill, H. A. Klein and W. R. C. Rowley
Physical Review Letters 78, 1876 – 1879 (1997)

Optically pumped 3He NMR and atomic hydrogen ESR at 0.6 T
J. L. Flowers, C. J. Bickley, P. W. Josephs-Franks and B. W. Petley
IEEE Transactions on Instrumentation and Measurement 46, 104 – 107 (1997)

Clearly resolved secular sidebands on the 2S1/22D5/2 674-nm clock transition in a single trapped Sr+ ion
G. P. Barwood, P. Gill, H. A. Klein and W. R. C. Rowley
IEEE Transactions on Instrumentation and Measurement 46, 133 – 136 (1997)

 

1996

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Calculation of hyperfine structure constants of the 127I2 R(39) 7 – 4 transition at 637 nm
S. Picard, A. Razet, C. S. Edwards and F. Rodriguez-Llorente
Metrologia 33, 569 – 572 (1996)

Frequency-stabilised diode lasers in the visible region using Doppler-free iodine spectra
C. S. Edwards, G. P. Barwood, P. Gill, F. Rodriguez-Llorente and W. R. C. Rowley
Optics Communications 132, 94 – 100 (1996)

 

1995

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Studies of trapped strontium ions in low magnetic fields
G. P. Barwood, P. Gill, G. Huang, H. A. Klein and W. R. C. Rowley
Applied Physics B 61, 385 – 390 (1995)

Absolute frequency stabilisation of a 637 nm laser diode using Doppler-free I2 spectra
C. S. Edwards, G. P. Barwood, P. Gill and W. R. C. Rowley
Electronics Letters 31, 796 – 797 (1995)

Measurement of the 2S1/22D5/2 411-nm interval in laser-cooled trapped 172Yb+ ions
P. Gill, H. A. Klein, A. P. Levick, M. Roberts, W. R. C. Rowley and P. Taylor
Physical Review A 52, R909 – R912 (1995)

Precision interferometric frequency measurement of the 674 nm 2S1/22D5/2 transition in a single cold Sr+ ion
G. P. Barwood, C. S. Edwards, P. Gill, G. Huang, H. A. Klein and W. R. C. Rowley
IEEE Transactions on Instrumentation and Measurement 44, 117 – 119 (1995)

Correcting high precision pulsed NMR flux density measurements for asymmetries in the lineshape
J. L. Flowers, P. W. Franks and B. W. Petley
IEEE Transactions on Instrumentation and Measurement 44, 488 – 490 (1995)

Optically pumped 3He NMR and the Bohr magneton
J. L. Flowers, P. W. Franks and B. W. Petley
IEEE Transactions on Instrumentation and Measurement 44, 572 – 574 (1995)

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