J. R. Torgerson

Limit on the temporal variation of the fine-structure constant using atomic dysprosium

Over 8 months, we monitored transition frequencies between nearly degenerate, opposite-parity levels in two isotopes of atomic dysprosium (Dy). These frequencies are sensitive to variation of the fine-structure constant (alpha) due to relativistic corrections of opposite sign for the opposite-parity levels. In this unique system, in contrast to atomic-clock comparisons, the difference of the electronic energies of the opposite-parity levels can be monitored directly utilizing a rf electric-dipole transition between them. Our measurements show that the frequency variation of the 3.1-MHz transition in (163)Dy and the 235-MHz transition in (162)Dy are 9.0+/-6.7 Hz/yr and -0.6+/-6.5 Hz/yr, respectively. These results provide a rate of fractional variation of alpha of (-2.7+/-2.6) x 10(-15) yr(-1) (1 sigma) without assumptions on constancy of other fundamental constants, indicating absence of significant variation at the present level of sensitivity.

New limits on variation of the fine-structure constant using atomic dysprosium.

We report on the spectroscopy of radio-frequency transitions between nearly degenerate, opposite-parity excited states in atomic dysprosium (Dy). Theoretical calculations predict that these states are very sensitive to variation of the fine-structure constant α owing to large relativistic corrections of opposite sign for the opposite-parity levels. The near degeneracy reduces the relative precision necessary to place constraints on variation of α, competitive with results obtained from the best atomic clocks in the world. Additionally, the existence of several abundant isotopes of Dy allows isotopic comparisons that suppress common-mode systematic errors. The frequencies of the 754-MHz transition in 164Dy and 235-MHz transition in 162Dy are measured over the span of two years. The linear variation of α is α·/α=(-5.8±6.9([1σ]))×10(-17)  yr(-1), consistent with zero. The same data are used to constrain the dimensionless parameter kα characterizing a possible coupling of α to a changing gravitational potential. We find that kα=(-5.5±5.2([1σ]))×10(-7), essentially consistent with zero and the best constraint to date.

Progress towards fabrication of 229Th-doped high energy band-gap crystals for use as a solid-state optical frequency reference

We have recently described a novel method for the construction of a solid-state optical frequency reference based on doping 229Th into high energy band-gap crystals [1]. Since nuclear transitions are far less sensitive to environmental conditions than atomic transitions, we have argued that the 229Th optical nuclear transition may be driven inside a host crystal resulting in an optical frequency reference with a short-term stability of 3 × 10−17 < Δf/f < 1 × 10−15 at 1 s and a systematic-limited repeatability of Δf/f ~2 × 10−16. Improvement by 102 – 103 of the constraints on the variability of several important fundamental constants also appears possible. Here we present the results of the first phase of these experiments. Specifically, we have evaluated several high energy band-gap crystals (Th:NaYF, Th:YLF, Th:LiCAF, Na2ThF6, LiSAF) for their suitability as a crystal host by a combination of electron beam microprobe measurements, Rutherford Backscattering, and synchrotron excitation/fluorescence measurements. These measurements have shown LiCAF to be the most promising host crystal, and using a 232Th doped LiCAF crystal, we have performed a mock run of the actual experiment that will be used to search for the isomeric transition in 229Th. This data indicates that a measurement of the transition energy with a signal to noise ratio (SNR) greater than 30:1 can be achieved at the lowest expected fluorescence rate.

Investigation of the gravitational-potential dependence of the fine-structure constant using atomic dysprosium

Radio-frequency E1 transitions between nearly degenerate, opposite-parity levels of atomic dysprosium (Dy) were monitored over an 8-month period to search for a variation in the fine-structure constant {alpha}. During this time period, data were taken at different points in the gravitational potential of the Sun. The data are fitted to the variation in the gravitational potential yielding a value of (-8.7{+-}6.6)x10{sup -6} for k{sub {alpha}}, the variation of {alpha} in a changing gravitational potential. This value gives the first laboratory limit independent of assumptions regarding other fundamental constants. In addition, our value of k{sub {alpha}} combined with other experimental constraints is used to extract the first limits on k{sub e} and k{sub q}. These coefficients characterize the variation of m{sub e}/m{sub p} and m{sub q}/m{sub p} in a changing gravitational potential, where m{sub e}, m{sub p}, and m{sub q} are electron, proton, and quark masses. The results are k{sub e}=(4.9{+-}3.9)x10{sup -5} and k{sub q}=(6.6{+-}5.2)x10{sup -5}. All these results indicate the absence of significant variation at the present level of sensitivity.

Towards a sensitive search for variation of the fine-structure constant using radio-frequency E1 transitions in atomic dysprosium

It has been proposed that the radio-frequency electric-dipole

Transverse laser cooling of a thermal atomic beam of dysprosium

(E1)

Extended temperature tuning of an ultraviolet diode laser for trapping and cooling single Yb+ ions

transition between two nearly degenerate opposite-parity states in atomic dysprosium should be highly sensitive to possible temporal variation of the fine-structure constant

New, efficient and robust, fiber-based quantum key distribution schemes

(\ensuremath{\alpha})

Transition frequency shifts with fine-structure constant variation for Yb II

[V. A. Dzuba, V. V. Flambaum, and J. K. Webb, Phys. Rev. A 59, 230 (1999)]. We analyze here an experimental realization of the proposed search in progress in our laboratory, which involves monitoring the

Isotope-selective trapping of doubly charged Yb ions

E1