Bulletin of the American Physical Society
39th Annual Meeting of the APS Division of Atomic, Molecular, and Optical Physics
Volume 53, Number 7
Tuesday–Saturday, May 27–31, 2008; State College, Pennsylvania
Session J2: Atomic Clocks and Searches for Variations in Fundamental Constants (Co-Sponsored by GPMFC) |
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Chair: Eric Burt, Jet Propulsion Laboratory Room: Kern Building 112 |
Thursday, May 29, 2008 11:00AM - 11:36AM |
J2.00001: Variation of fundamental constants: theory Invited Speaker: Theories unifying gravity with other interactions suggest temporal and spatial variation of the fundamental ``constants'' in expanding Universe. There are some hints for the variation of different fundamental constants in quasar absorption spectra and Big Bang nucleosynthesis data. A large number of publications (including atomic clocks) report limits on the variations. We want to study the variation of the main dimensionless parameters of the Standard Model: 1. Fine structure constant alpha (combination of speed of light, electron charge and Plank constant). 2. Ratio of the strong interaction scale (Lambda$_{QCD}$) to a fundamental mass like electron mass or quark mass which are proportional to Higgs vacuum expectation value. The proton mass is propotional to Lambda$_{QCD}$, therefore, the proton-to-electron mass ratio comes into this second category. We performed necessary atomic, nuclear and QCD calculations needed to study variation of the fundamental constants using the Big Bang Nucleosynthsis, quasar spectra, Oklo natural nuclear reactor and atomic clock data. The relative effects of the variation may be enhanced in transitions between narrow close levels in atoms, molecules and nuclei. If one will study an enhanced effect, the relative value of systematic effects (which are not enhanced) may be much smaller. Note also that the absolute magnitude of the variation effects in nuclei (e.g. in very narrow 7 eV transition in 229Th) may be 5 orders of magnitude larger than in atoms. A different possibility of enhancement comes from the inversion transitions in molecules where splitting between the levels is due to the quantum tunneling amplitude which has strong, exponential dependence on the electron to proton mass ratio. Our study of NH$_3$ quasar spectra has already given the best limit on the variation of electron to proton mass ratio. [Preview Abstract] |
Thursday, May 29, 2008 11:36AM - 12:12PM |
J2.00002: Search for Temporal Variation of Fundamental Constants With Hg+ and Al+ Optical Clocks Invited Speaker: \newcommand{\ratioAlHg}{$\sepnum{.}{\,}{\,}{1.052871833148990438} (55)$} \newcommand{\uncertaintyAlHg}{$5.2\times10^{-17}$} \newcommand{\uncertaintyAl}{$2.3\times10^{-17}$} \newcommand{\uncertaintyHg}{$1.9\times10^{-17}$} \newcommand{\uncertaintyHgCs}{$6.5\times10^{-16}$} \newcommand{\uncertaintyStat}{$4.3\times10^{-17}$} \newcommand{\absolutefreqAl}{$\sepnum{.}{\,}{\,} {1121015393207857.4}(7)$ Hz} \newcommand{\Al}{$^{27}$Al$^+$ } \newcommand{\Alns}{$^{27}$Al$^+$} \newcommand{\Be}{$^{9}$Be$^+$ } \newcommand{\Bens}{$^{9}$Be$^+$} \newcommand{\Hg}{$^{199}$Hg$^+$ } \newcommand{\Hgns}{$^{199}$Hg$^+$} \newcommand{\ratioName}{$\nu_{Al^+}/\nu_{Hg^+}$ } \newcommand{\alphadotConstraint}{$\dot{\alpha}/\alpha = (-1.6 \pm 2.4) \times 10^{-17} /$year} We measure the ratio of aluminum and mercury single-ion optical clock frequencies with a fractional uncertainty of \uncertaintyAlHg, comprising a statistical measurement uncertainty of \uncertaintyStat, and systematic uncertainties of \uncertaintyHg$ $ and \uncertaintyAl$ $ in the mercury and aluminum frequency standards, respectively. This frequency ratio is the best known physical constant that is not a simple integer. Repeated measurements during the past year yield a preliminary constraint on the temporal variation of the fine-structure constant of \alphadotConstraint. [Preview Abstract] |
Thursday, May 29, 2008 12:12PM - 12:48PM |
J2.00003: Search for Temporal Variations in Alpha Using a Yb$^+$ Optical Frequency Standard Invited Speaker: Optical frequency standards based on forbidden transitions of trapped and laser-cooled ions have now achieved significantly higher stability and also greater accuracy than primary cesium clocks. At PTB we investigate an optical clock based on the electric quadrupole transition $S_{1/2} - D_{3/2}$ at 688 THz in the $^{171}$Yb$^+$ ion and have shown that the frequencies realized in two independent ion traps agree to within a few parts in $10^{16}$. Results from a sequence of precise measurements of the absolute transition frequency are now available that cover a period of seven years. Combined with data obtained at NIST on the quadrupole transition in Hg$^+$, this allows to derive a model-independent limit for a temporal drift of the fine structure constant alpha. We prepare to observe the electric-octupole transition $S_{1/2} - F_{7/2}$ of Yb$^+$ at 642 THz with sub-hertz resolution. This narrow-linewidth reference transition promises a reduced quantum-noise limited instability of the single-ion optical clock. The ratio of the 688 THz and 642 THz reference frequencies can be measured as a dimensionless number with a femtosecond laser frequency comb, independent from the realization of the SI second with cesium clocks. Repeated measurements of this quantity permit to search for temporal variations of alpha with increased sensitivity. [Preview Abstract] |
Thursday, May 29, 2008 12:48PM - 1:24PM |
J2.00004: Search for Temporal Variations in Fundamental Constants Using Hyperfine Transitions in Primary Atomic Clocks Invited Speaker: We will report on recent work performed with LNE-SYRTE fountain ensemble. This fountain ensemble includes a Cs fountain FO1, a transportable Cs fountain FOM and a dual fountain FO2, operating both with Rb and Cs. These three fountains are using the same ultra low phase noise interrogation oscillator based on a continuously operated cryogenic sapphire resonator oscillator (CSO), leading to best short term fractional frequency instabilities ranging from 1.6 to 6 parts in 1014. Recent work with FO2 focused on improving the rubidium part to reach accuracy similar to those achieved with Cs fountains ($!$4 to 12 parts in 1016). Recent comparisons in November 2007 with FOM show fractional frequency instability down to 3 parts in 1016 at 2 days. These comparisons provide new measurements of the Rb hyperfine frequency and improve the test of the variation of fundamental constants based on comparing the Rb and Cs hyperfine frequency over time. This work was performed in collaboration with Jocelyne Guena, Frederic Chapelet, Peter Rosenbusch, Philippe Laurent, Michel Abgrall, Daniele Rovera, Giorgio Santarelli, Lne-Syrte and Michael Tobar, University of Western Australia; and Andre Clairon, LNE-SYRTE-Observatoire de Paris. [Preview Abstract] |
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